sp-acj4-130-cond true

category simplipy-conditional

Summary

Given

\(x \in \mathbb{R},\quad \left|x\right| < \frac{\pi}{2},\quad \cos x \neq 0,\quad \frac{1}{\cos x} \neq 0\)

Claim

\(\displaystyle \left|\log\left(\cos x\right)\right| = \log\left(\frac{1}{\cos x}\right)\)

Expected

true equal at every admissible point

the two sides are equal at every admissible point

SimpliPy acj-4 (MIT) rules_real.json[130]: abs log cos _0 -> log inv cos _0 [weakest assumption found: abs-lt-pi2]

Lean proof: included

Answers (latest run per system; open code for the reproducer that ran)

system outcome answer steps (from the trace) s run query (as sent) detail

none

always-none no verdict null 0.0 2026-10-13 17:21:18 ba9dc4def822 (real x) ∧ (< (abs x) (/ pi 2)) ∧ (nonzero (cos x)) ∧ (nonzero (/ (cos x))) ⊢ (= (abs (log (cos x))) (log (/ (cos x)))) null

sympy

sympy-ask no verdict null difference → -log(1/cos(x)) + Abs(log(cos(x))) · ask → None 0.552 2026-10-13 17:21:19 ba9dc4def822 Q.real(x) ∧ (Abs(x) < (pi/2)) ∧ (~Q.zero(cos(x))) ∧ (~Q.zero((1/cos(x)))) ⊢ Eq(Abs(log(cos(x))), log((1/cos(x)))) null

code

setup — not timed

from sympy import *
import sympy

SympyVersion = sympy.__version__
# warm-up: a fixed generic expression, never case content
W = Symbol('W')
Warmup = ask(Q.positive(W**2 + 1), Q.real(W))
# every query then runs in its own forked process, starting from this state:
# the expression caches are dropped (imported and lazily loaded modules stay)
sympy.core.cache.clear_cache()

x = Symbol('x', real=True)
Assum = And(Q.real(x), Abs(x) < pi / 2, ~Q.zero(cos(x)), ~Q.zero(1 / cos(x)))
Residual = Abs(log(cos(x))) - log(1 / cos(x))
# not Q.eq: in SymPy 1.14 ask(Q.eq(x**2, x), Q.real(x)) is wrongly False
Answer = ask(Q.zero(Residual), Assum)
print(Residual, Answer, sep='\n')

difference	`Abs(log(cos(x))) - log(1 / cos(x))`	→	`-log(1/cos(x)) + Abs(log(cos(x)))`
ask	`Q.zero(Residual)`	→	`None`
answer			`null`

sympy-ask no verdict null difference → -log(1/cos(x)) + Abs(log(cos(x))) · ask → None 0.048 2026-10-12 21:54:02 ee702ae2fe06 Q.real(x) ∧ (Abs(x) < (pi/2)) ∧ (~Q.zero(cos(x))) ∧ (~Q.zero((1/cos(x)))) ⊢ Eq(Abs(log(cos(x))), log((1/cos(x)))) null

code

setup — not timed

from sympy import *
import sympy

SympyVersion = sympy.__version__
# warm-up: a fixed generic expression, never case content
W = Symbol('W')
Warmup = ask(Q.positive(W**2 + 1), Q.real(W))
# every query then runs in its own forked process, starting from this state:
# the expression caches are dropped (imported and lazily loaded modules stay)
sympy.core.cache.clear_cache()

x = Symbol('x', real=True)
Assum = And(Q.real(x), Abs(x) < pi / 2, ~Q.zero(cos(x)), ~Q.zero(1 / cos(x)))
Residual = Abs(log(cos(x))) - log(1 / cos(x))
# not Q.eq: in SymPy 1.14 ask(Q.eq(x**2, x), Q.real(x)) is wrongly False
Answer = ask(Q.zero(Residual), Assum)
print(Residual, Answer, sep='\n')

difference	`Abs(log(cos(x))) - log(1 / cos(x))`	→	`-log(1/cos(x)) + Abs(log(cos(x)))`
ask	`Q.zero(Residual)`	→	`None`
answer			`null`

sympy-refine no verdict null difference → -log(1/cos(x)) + Abs(log(cos(x))) · refine → -log(1/cos(x)) + Abs(log(cos(x))) 0.089 2026-10-13 17:22:30 ba9dc4def822 Q.real(x) ∧ (Abs(x) < (pi/2)) ∧ (~Q.zero(cos(x))) ∧ (~Q.zero((1/cos(x)))) ⊢ Eq(Abs(log(cos(x))), log((1/cos(x)))) null

code

setup — not timed

from sympy import *
import sympy

SympyVersion = sympy.__version__
# warm-up: a fixed generic expression, never case content
W = Symbol('W')
Warmup = refine(Abs(W), Q.positive(W))
# every query then runs in its own forked process, starting from this state:
# the expression caches are dropped (imported and lazily loaded modules stay)
sympy.core.cache.clear_cache()

x = Symbol('x', real=True)
Assum = And(Q.real(x), Abs(x) < pi / 2, ~Q.zero(cos(x)), ~Q.zero(1 / cos(x)))
Residual = Abs(log(cos(x))) - log(1 / cos(x))
Result = refine(Residual, Assum)
# true iff the result is 0; false only if it is a definite nonzero number
Answer = True if Result == 0 else False if (Result.is_number and Result.is_finite and Result.is_zero is False) else None
print(Result, Answer, sep='\n')

difference	`Abs(log(cos(x))) - log(1 / cos(x))`	→	`-log(1/cos(x)) + Abs(log(cos(x)))`
refine	`refine(Residual, Assum)`	→	`-log(1/cos(x)) + Abs(log(cos(x)))`
answer			`null`

sympy-refine no verdict null difference → -log(1/cos(x)) + Abs(log(cos(x))) · refine → -log(1/cos(x)) + Abs(log(cos(x))) 0.092 2026-10-12 21:54:16 ee702ae2fe06 Q.real(x) ∧ (Abs(x) < (pi/2)) ∧ (~Q.zero(cos(x))) ∧ (~Q.zero((1/cos(x)))) ⊢ Eq(Abs(log(cos(x))), log((1/cos(x)))) null

code

setup — not timed

from sympy import *
import sympy

SympyVersion = sympy.__version__
# warm-up: a fixed generic expression, never case content
W = Symbol('W')
Warmup = refine(Abs(W), Q.positive(W))
# every query then runs in its own forked process, starting from this state:
# the expression caches are dropped (imported and lazily loaded modules stay)
sympy.core.cache.clear_cache()

x = Symbol('x', real=True)
Assum = And(Q.real(x), Abs(x) < pi / 2, ~Q.zero(cos(x)), ~Q.zero(1 / cos(x)))
Residual = Abs(log(cos(x))) - log(1 / cos(x))
Result = refine(Residual, Assum)
# true iff the result is 0; false only if it is a definite nonzero number
Answer = True if Result == 0 else False if (Result.is_number and Result.is_finite and Result.is_zero is False) else None
print(Result, Answer, sep='\n')

difference	`Abs(log(cos(x))) - log(1 / cos(x))`	→	`-log(1/cos(x)) + Abs(log(cos(x)))`
refine	`refine(Residual, Assum)`	→	`-log(1/cos(x)) + Abs(log(cos(x)))`
answer			`null`

sympy-simplify no verdict null difference → -log(1/cos(x)) + Abs(log(cos(x))) · simplify → -log(1/cos(x)) + Abs(log(cos(x))) 0.061 2026-10-13 17:24:01 ba9dc4def822 Q.real(x) ∧ (Abs(x) < (pi/2)) ∧ (~Q.zero(cos(x))) ∧ (~Q.zero((1/cos(x)))) ⊢ Eq(Abs(log(cos(x))), log((1/cos(x)))) null

code

setup — not timed

from sympy import *
import sympy

SympyVersion = sympy.__version__
# warm-up: a fixed generic expression, never case content
W = Symbol('W')
Warmup = simplify(sin(W)**2 + cos(W)**2)
# every query then runs in its own forked process, starting from this state:
# the expression caches are dropped (imported and lazily loaded modules stay)
sympy.core.cache.clear_cache()

x = Symbol('x', real=True)
# dropped (not a unary fact about one symbol): Abs(x) < pi / 2
# dropped (not a unary fact about one symbol): ~Q.zero(cos(x))
# dropped (not a unary fact about one symbol): ~Q.zero(1 / cos(x))
Residual = Abs(log(cos(x))) - log(1 / cos(x))
Result = simplify(Residual)
# true iff the result is 0; false only if it is a definite nonzero number
Answer = True if Result == 0 else False if (Result.is_number and Result.is_finite and Result.is_zero is False) else None
print(Result, Answer, sep='\n')

difference	`Abs(log(cos(x))) - log(1 / cos(x))`	→	`-log(1/cos(x)) + Abs(log(cos(x)))`
simplify	`simplify(Residual)`	→	`-log(1/cos(x)) + Abs(log(cos(x)))`
answer			`null`

sympy-simplify no verdict null difference → -log(1/cos(x)) + Abs(log(cos(x))) · simplify → -log(1/cos(x)) + Abs(log(cos(x))) 0.065 2026-10-12 21:54:43 ee702ae2fe06 Q.real(x) ∧ (Abs(x) < (pi/2)) ∧ (~Q.zero(cos(x))) ∧ (~Q.zero((1/cos(x)))) ⊢ Eq(Abs(log(cos(x))), log((1/cos(x)))) null

code

setup — not timed

from sympy import *
import sympy

SympyVersion = sympy.__version__
# warm-up: a fixed generic expression, never case content
W = Symbol('W')
Warmup = simplify(sin(W)**2 + cos(W)**2)
# every query then runs in its own forked process, starting from this state:
# the expression caches are dropped (imported and lazily loaded modules stay)
sympy.core.cache.clear_cache()

x = Symbol('x', real=True)
# dropped (not a unary fact about one symbol): Abs(x) < pi / 2
# dropped (not a unary fact about one symbol): ~Q.zero(cos(x))
# dropped (not a unary fact about one symbol): ~Q.zero(1 / cos(x))
Residual = Abs(log(cos(x))) - log(1 / cos(x))
Result = simplify(Residual)
# true iff the result is 0; false only if it is a definite nonzero number
Answer = True if Result == 0 else False if (Result.is_number and Result.is_finite and Result.is_zero is False) else None
print(Result, Answer, sep='\n')

difference	`Abs(log(cos(x))) - log(1 / cos(x))`	→	`-log(1/cos(x)) + Abs(log(cos(x)))`
simplify	`simplify(Residual)`	→	`-log(1/cos(x)) + Abs(log(cos(x)))`
answer			`null`

wolfram

wolfram-fullsimplify solved true difference → Abs[Log[Cos[x]]] - Log[Sec[x]] · result → 0 0.149 2026-10-13 17:24:42 ba9dc4def822 Element[x, Reals] ∧ (Abs[x] < (Pi/2)) ∧ (Cos[x] != 0) ∧ ((1/Cos[x]) != 0) ⊢ (Abs[Log[Cos[x]]] == Log[(1/Cos[x])]) true

code

setup — not timed

(
  $HistoryLength = 0;
  $Messages = {};
  Warmup = FullSimplify[Sin[W]^2 + Cos[W]^2, Element[W, Reals]];
  GenericWarmup = Quiet[{Simplify[Abs[W] + W, W < 0], Simplify[Sqrt[W^2] - W, W > 0], Refine[Sqrt[W^2], W > 0], Simplify[Log[W V] - Log[W] - Log[V], W > 0 && V > 0], Simplify[Log[-W] - Log[W] - I Pi, W < 0], Simplify[(-1)^(2 W) - 1, Element[W, Integers]], Simplify[Mod[W + 1, 2], Element[W, Integers] && Element[(W - 1)/2, Integers]], Simplify[ArcTan[W] + ArcTan[1/W] - Pi/2, W > 0], FullSimplify[ArcCot[W] - ArcTan[1/W], W > 0], Simplify[Abs[Exp[I W]] - 1, Element[W, Reals]], Simplify[Re[W] - (W + Conjugate[W])/2], Simplify[Gamma[W + 1] - W!, Element[W, Integers] && W > 0], Simplify[Floor[W] - W, Element[W, Integers]], Simplify[Sqrt[W] Sqrt[V] - Sqrt[W V], W > 0 && V > 0], Simplify[HeavisideTheta[W] - 1, W > 0], Simplify[2^W 2^V - 2^(W + V), Element[W, Reals] && Element[V, Reals]], Simplify[Sum[V, {V, 1, W}] - W (W + 1)/2, Element[W, Integers] && W > 0]}];
  Quiet[Check[Message[General::argx, "W", 0], Null]];
  {$Version, Warmup, Length[GenericWarmup]}
)

(* evaluated in a forked copy of the setup kernel: TimeConstrained would not fire here (no timer thread), so the parent enforces a hard timeout of 9 s by killing this process *)
(
  Assum = (Element[x, Reals]) && ((Abs[x] < (Pi/2))) && ((Cos[x] != 0)) && (((1/Cos[x]) != 0));
  Residual = (Abs[Log[Cos[x]]]) - (Log[1/Cos[x]]);
  Result = FullSimplify[Residual, Assum];
  Answer = Which[Result === 0, True, NumericQ[Result] && TrueQ[Result != 0], False, True, Null];
  {Residual, Result, Answer}
)

difference	`(Abs[Log[Cos[x]]]) - (Log[1/Cos[x]])`	→	`Abs[Log[Cos[x]]] - Log[Sec[x]]`
result	`FullSimplify[Residual, Assum]`	→	`0`
answer			`true`

wolfram-refine no verdict null difference → Abs[Log[Cos[x]]] - Log[Sec[x]] · result → -Log[Cos[x]] - Log[Sec[x]] 0.037 2026-10-13 17:24:31 ba9dc4def822 Element[x, Reals] ∧ (Abs[x] < (Pi/2)) ∧ (Cos[x] != 0) ∧ ((1/Cos[x]) != 0) ⊢ (Abs[Log[Cos[x]]] == Log[(1/Cos[x])]) null

code

setup — not timed

(
  $HistoryLength = 0;
  $Messages = {};
  Warmup = Refine[Sin[W]^2 + Cos[W]^2, Element[W, Reals]];
  GenericWarmup = Quiet[{Simplify[Abs[W] + W, W < 0], Simplify[Sqrt[W^2] - W, W > 0], Refine[Sqrt[W^2], W > 0], Simplify[Log[W V] - Log[W] - Log[V], W > 0 && V > 0], Simplify[Log[-W] - Log[W] - I Pi, W < 0], Simplify[(-1)^(2 W) - 1, Element[W, Integers]], Simplify[Mod[W + 1, 2], Element[W, Integers] && Element[(W - 1)/2, Integers]], Simplify[ArcTan[W] + ArcTan[1/W] - Pi/2, W > 0], FullSimplify[ArcCot[W] - ArcTan[1/W], W > 0], Simplify[Abs[Exp[I W]] - 1, Element[W, Reals]], Simplify[Re[W] - (W + Conjugate[W])/2], Simplify[Gamma[W + 1] - W!, Element[W, Integers] && W > 0], Simplify[Floor[W] - W, Element[W, Integers]], Simplify[Sqrt[W] Sqrt[V] - Sqrt[W V], W > 0 && V > 0], Simplify[HeavisideTheta[W] - 1, W > 0], Simplify[2^W 2^V - 2^(W + V), Element[W, Reals] && Element[V, Reals]], Simplify[Sum[V, {V, 1, W}] - W (W + 1)/2, Element[W, Integers] && W > 0]}];
  Quiet[Check[Message[General::argx, "W", 0], Null]];
  {$Version, Warmup, Length[GenericWarmup]}
)

(* evaluated in a forked copy of the setup kernel: TimeConstrained would not fire here (no timer thread), so the parent enforces a hard timeout of 9 s by killing this process *)
(
  Assum = (Element[x, Reals]) && ((Abs[x] < (Pi/2))) && ((Cos[x] != 0)) && (((1/Cos[x]) != 0));
  Residual = (Abs[Log[Cos[x]]]) - (Log[1/Cos[x]]);
  Result = Refine[Residual, Assum];
  Answer = Which[Result === 0, True, NumericQ[Result] && TrueQ[Result != 0], False, True, Null];
  {Residual, Result, Answer}
)

difference	`(Abs[Log[Cos[x]]]) - (Log[1/Cos[x]])`	→	`Abs[Log[Cos[x]]] - Log[Sec[x]]`
result	`Refine[Residual, Assum]`	→	`-Log[Cos[x]] - Log[Sec[x]]`
answer			`null`

wolfram-simplify no verdict null difference → Abs[Log[Cos[x]]] - Log[Sec[x]] · result → Abs[Log[Cos[x]]] - Log[Sec[x]] 0.257 2026-10-13 17:24:17 ba9dc4def822 Element[x, Reals] ∧ (Abs[x] < (Pi/2)) ∧ (Cos[x] != 0) ∧ ((1/Cos[x]) != 0) ⊢ (Abs[Log[Cos[x]]] == Log[(1/Cos[x])]) null

code

setup — not timed

(
  $HistoryLength = 0;
  $Messages = {};
  Warmup = Simplify[Sin[W]^2 + Cos[W]^2, Element[W, Reals]];
  GenericWarmup = Quiet[{Simplify[Abs[W] + W, W < 0], Simplify[Sqrt[W^2] - W, W > 0], Refine[Sqrt[W^2], W > 0], Simplify[Log[W V] - Log[W] - Log[V], W > 0 && V > 0], Simplify[Log[-W] - Log[W] - I Pi, W < 0], Simplify[(-1)^(2 W) - 1, Element[W, Integers]], Simplify[Mod[W + 1, 2], Element[W, Integers] && Element[(W - 1)/2, Integers]], Simplify[ArcTan[W] + ArcTan[1/W] - Pi/2, W > 0], FullSimplify[ArcCot[W] - ArcTan[1/W], W > 0], Simplify[Abs[Exp[I W]] - 1, Element[W, Reals]], Simplify[Re[W] - (W + Conjugate[W])/2], Simplify[Gamma[W + 1] - W!, Element[W, Integers] && W > 0], Simplify[Floor[W] - W, Element[W, Integers]], Simplify[Sqrt[W] Sqrt[V] - Sqrt[W V], W > 0 && V > 0], Simplify[HeavisideTheta[W] - 1, W > 0], Simplify[2^W 2^V - 2^(W + V), Element[W, Reals] && Element[V, Reals]], Simplify[Sum[V, {V, 1, W}] - W (W + 1)/2, Element[W, Integers] && W > 0]}];
  Quiet[Check[Message[General::argx, "W", 0], Null]];
  {$Version, Warmup, Length[GenericWarmup]}
)

(* evaluated in a forked copy of the setup kernel: TimeConstrained would not fire here (no timer thread), so the parent enforces a hard timeout of 9 s by killing this process *)
(
  Assum = (Element[x, Reals]) && ((Abs[x] < (Pi/2))) && ((Cos[x] != 0)) && (((1/Cos[x]) != 0));
  Residual = (Abs[Log[Cos[x]]]) - (Log[1/Cos[x]]);
  Result = Simplify[Residual, Assum];
  Answer = Which[Result === 0, True, NumericQ[Result] && TrueQ[Result != 0], False, True, Null];
  {Residual, Result, Answer}
)

difference	`(Abs[Log[Cos[x]]]) - (Log[1/Cos[x]])`	→	`Abs[Log[Cos[x]]] - Log[Sec[x]]`
result	`Simplify[Residual, Assum]`	→	`Abs[Log[Cos[x]]] - Log[Sec[x]]`
answer			`null`

Older runs (11)

system outcome answer steps (from the trace) s run query (as sent) detail

wolfram-fullsimplify solved true difference → Abs[Log[Cos[x]]] - Log[Sec[x]] · result → 0 0.152 2026-10-13 16:43:00 3ba0dfac4bca Element[x, Reals] ∧ (Abs[x] < (Pi/2)) ∧ (Cos[x] != 0) ∧ ((1/Cos[x]) != 0) ⊢ (Abs[Log[Cos[x]]] == Log[(1/Cos[x])]) true

code

setup — not timed

(
  $HistoryLength = 0;
  $Messages = {};
  Warmup = FullSimplify[Sin[W]^2 + Cos[W]^2, Element[W, Reals]];
  GenericWarmup = Quiet[{Simplify[Abs[W] + W, W < 0], Simplify[Sqrt[W^2] - W, W > 0], Refine[Sqrt[W^2], W > 0], Simplify[Log[W V] - Log[W] - Log[V], W > 0 && V > 0], Simplify[Log[-W] - Log[W] - I Pi, W < 0], Simplify[(-1)^(2 W) - 1, Element[W, Integers]], Simplify[Mod[W + 1, 2], Element[W, Integers] && Element[(W - 1)/2, Integers]], Simplify[ArcTan[W] + ArcTan[1/W] - Pi/2, W > 0], FullSimplify[ArcCot[W] - ArcTan[1/W], W > 0], Simplify[Abs[Exp[I W]] - 1, Element[W, Reals]], Simplify[Re[W] - (W + Conjugate[W])/2], Simplify[Gamma[W + 1] - W!, Element[W, Integers] && W > 0], Simplify[Floor[W] - W, Element[W, Integers]], Simplify[Sqrt[W] Sqrt[V] - Sqrt[W V], W > 0 && V > 0], Simplify[HeavisideTheta[W] - 1, W > 0], Simplify[2^W 2^V - 2^(W + V), Element[W, Reals] && Element[V, Reals]], Simplify[Sum[V, {V, 1, W}] - W (W + 1)/2, Element[W, Integers] && W > 0]}];
  Quiet[Check[Message[General::argx, "W", 0], Null]];
  {$Version, Warmup, Length[GenericWarmup]}
)

(* evaluated in a forked copy of the setup kernel: TimeConstrained would not fire here (no timer thread), so the parent enforces a hard timeout of 9 s by killing this process *)
(
  Assum = (Element[x, Reals]) && ((Abs[x] < (Pi/2))) && ((Cos[x] != 0)) && (((1/Cos[x]) != 0));
  Residual = (Abs[Log[Cos[x]]]) - (Log[1/Cos[x]]);
  Result = FullSimplify[Residual, Assum];
  Answer = Which[Result === 0, True, NumericQ[Result] && TrueQ[Result != 0], False, True, Null];
  {Residual, Result, Answer}
)

difference	`(Abs[Log[Cos[x]]]) - (Log[1/Cos[x]])`	→	`Abs[Log[Cos[x]]] - Log[Sec[x]]`
result	`FullSimplify[Residual, Assum]`	→	`0`
answer			`true`

wolfram-refine no verdict null difference → Abs[Log[Cos[x]]] - Log[Sec[x]] · result → -Log[Cos[x]] - Log[Sec[x]] 0.038 2026-10-13 16:42:50 3ba0dfac4bca Element[x, Reals] ∧ (Abs[x] < (Pi/2)) ∧ (Cos[x] != 0) ∧ ((1/Cos[x]) != 0) ⊢ (Abs[Log[Cos[x]]] == Log[(1/Cos[x])]) null

code

setup — not timed

(
  $HistoryLength = 0;
  $Messages = {};
  Warmup = Refine[Sin[W]^2 + Cos[W]^2, Element[W, Reals]];
  GenericWarmup = Quiet[{Simplify[Abs[W] + W, W < 0], Simplify[Sqrt[W^2] - W, W > 0], Refine[Sqrt[W^2], W > 0], Simplify[Log[W V] - Log[W] - Log[V], W > 0 && V > 0], Simplify[Log[-W] - Log[W] - I Pi, W < 0], Simplify[(-1)^(2 W) - 1, Element[W, Integers]], Simplify[Mod[W + 1, 2], Element[W, Integers] && Element[(W - 1)/2, Integers]], Simplify[ArcTan[W] + ArcTan[1/W] - Pi/2, W > 0], FullSimplify[ArcCot[W] - ArcTan[1/W], W > 0], Simplify[Abs[Exp[I W]] - 1, Element[W, Reals]], Simplify[Re[W] - (W + Conjugate[W])/2], Simplify[Gamma[W + 1] - W!, Element[W, Integers] && W > 0], Simplify[Floor[W] - W, Element[W, Integers]], Simplify[Sqrt[W] Sqrt[V] - Sqrt[W V], W > 0 && V > 0], Simplify[HeavisideTheta[W] - 1, W > 0], Simplify[2^W 2^V - 2^(W + V), Element[W, Reals] && Element[V, Reals]], Simplify[Sum[V, {V, 1, W}] - W (W + 1)/2, Element[W, Integers] && W > 0]}];
  Quiet[Check[Message[General::argx, "W", 0], Null]];
  {$Version, Warmup, Length[GenericWarmup]}
)

(* evaluated in a forked copy of the setup kernel: TimeConstrained would not fire here (no timer thread), so the parent enforces a hard timeout of 9 s by killing this process *)
(
  Assum = (Element[x, Reals]) && ((Abs[x] < (Pi/2))) && ((Cos[x] != 0)) && (((1/Cos[x]) != 0));
  Residual = (Abs[Log[Cos[x]]]) - (Log[1/Cos[x]]);
  Result = Refine[Residual, Assum];
  Answer = Which[Result === 0, True, NumericQ[Result] && TrueQ[Result != 0], False, True, Null];
  {Residual, Result, Answer}
)

difference	`(Abs[Log[Cos[x]]]) - (Log[1/Cos[x]])`	→	`Abs[Log[Cos[x]]] - Log[Sec[x]]`
result	`Refine[Residual, Assum]`	→	`-Log[Cos[x]] - Log[Sec[x]]`
answer			`null`

wolfram-simplify no verdict null difference → Abs[Log[Cos[x]]] - Log[Sec[x]] · result → Abs[Log[Cos[x]]] - Log[Sec[x]] 0.252 2026-10-13 16:42:35 3ba0dfac4bca Element[x, Reals] ∧ (Abs[x] < (Pi/2)) ∧ (Cos[x] != 0) ∧ ((1/Cos[x]) != 0) ⊢ (Abs[Log[Cos[x]]] == Log[(1/Cos[x])]) null

code

setup — not timed

(
  $HistoryLength = 0;
  $Messages = {};
  Warmup = Simplify[Sin[W]^2 + Cos[W]^2, Element[W, Reals]];
  GenericWarmup = Quiet[{Simplify[Abs[W] + W, W < 0], Simplify[Sqrt[W^2] - W, W > 0], Refine[Sqrt[W^2], W > 0], Simplify[Log[W V] - Log[W] - Log[V], W > 0 && V > 0], Simplify[Log[-W] - Log[W] - I Pi, W < 0], Simplify[(-1)^(2 W) - 1, Element[W, Integers]], Simplify[Mod[W + 1, 2], Element[W, Integers] && Element[(W - 1)/2, Integers]], Simplify[ArcTan[W] + ArcTan[1/W] - Pi/2, W > 0], FullSimplify[ArcCot[W] - ArcTan[1/W], W > 0], Simplify[Abs[Exp[I W]] - 1, Element[W, Reals]], Simplify[Re[W] - (W + Conjugate[W])/2], Simplify[Gamma[W + 1] - W!, Element[W, Integers] && W > 0], Simplify[Floor[W] - W, Element[W, Integers]], Simplify[Sqrt[W] Sqrt[V] - Sqrt[W V], W > 0 && V > 0], Simplify[HeavisideTheta[W] - 1, W > 0], Simplify[2^W 2^V - 2^(W + V), Element[W, Reals] && Element[V, Reals]], Simplify[Sum[V, {V, 1, W}] - W (W + 1)/2, Element[W, Integers] && W > 0]}];
  Quiet[Check[Message[General::argx, "W", 0], Null]];
  {$Version, Warmup, Length[GenericWarmup]}
)

(* evaluated in a forked copy of the setup kernel: TimeConstrained would not fire here (no timer thread), so the parent enforces a hard timeout of 9 s by killing this process *)
(
  Assum = (Element[x, Reals]) && ((Abs[x] < (Pi/2))) && ((Cos[x] != 0)) && (((1/Cos[x]) != 0));
  Residual = (Abs[Log[Cos[x]]]) - (Log[1/Cos[x]]);
  Result = Simplify[Residual, Assum];
  Answer = Which[Result === 0, True, NumericQ[Result] && TrueQ[Result != 0], False, True, Null];
  {Residual, Result, Answer}
)

difference	`(Abs[Log[Cos[x]]]) - (Log[1/Cos[x]])`	→	`Abs[Log[Cos[x]]] - Log[Sec[x]]`
result	`Simplify[Residual, Assum]`	→	`Abs[Log[Cos[x]]] - Log[Sec[x]]`
answer			`null`

sympy-simplify no verdict null difference → -log(1/cos(x)) + Abs(log(cos(x))) · simplify → -log(1/cos(x)) + Abs(log(cos(x))) 0.062 2026-10-13 16:42:18 3ba0dfac4bca Q.real(x) ∧ (Abs(x) < (pi/2)) ∧ (~Q.zero(cos(x))) ∧ (~Q.zero((1/cos(x)))) ⊢ Eq(Abs(log(cos(x))), log((1/cos(x)))) null

code

setup — not timed

from sympy import *
import sympy

SympyVersion = sympy.__version__
# warm-up: a fixed generic expression, never case content
W = Symbol('W')
Warmup = simplify(sin(W)**2 + cos(W)**2)
# every query then runs in its own forked process, starting from this state:
# the expression caches are dropped (imported and lazily loaded modules stay)
sympy.core.cache.clear_cache()

x = Symbol('x', real=True)
# dropped (not a unary fact about one symbol): Abs(x) < pi / 2
# dropped (not a unary fact about one symbol): ~Q.zero(cos(x))
# dropped (not a unary fact about one symbol): ~Q.zero(1 / cos(x))
Residual = Abs(log(cos(x))) - log(1 / cos(x))
Result = simplify(Residual)
# true iff the result is 0; false only if it is a definite nonzero number
Answer = True if Result == 0 else False if (Result.is_number and Result.is_finite and Result.is_zero is False) else None
print(Result, Answer, sep='\n')

difference	`Abs(log(cos(x))) - log(1 / cos(x))`	→	`-log(1/cos(x)) + Abs(log(cos(x)))`
simplify	`simplify(Residual)`	→	`-log(1/cos(x)) + Abs(log(cos(x)))`
answer			`null`

sympy-refine no verdict null difference → -log(1/cos(x)) + Abs(log(cos(x))) · refine → -log(1/cos(x)) + Abs(log(cos(x))) 0.088 2026-10-13 16:40:40 3ba0dfac4bca Q.real(x) ∧ (Abs(x) < (pi/2)) ∧ (~Q.zero(cos(x))) ∧ (~Q.zero((1/cos(x)))) ⊢ Eq(Abs(log(cos(x))), log((1/cos(x)))) null

code

setup — not timed

from sympy import *
import sympy

SympyVersion = sympy.__version__
# warm-up: a fixed generic expression, never case content
W = Symbol('W')
Warmup = refine(Abs(W), Q.positive(W))
# every query then runs in its own forked process, starting from this state:
# the expression caches are dropped (imported and lazily loaded modules stay)
sympy.core.cache.clear_cache()

x = Symbol('x', real=True)
Assum = And(Q.real(x), Abs(x) < pi / 2, ~Q.zero(cos(x)), ~Q.zero(1 / cos(x)))
Residual = Abs(log(cos(x))) - log(1 / cos(x))
Result = refine(Residual, Assum)
# true iff the result is 0; false only if it is a definite nonzero number
Answer = True if Result == 0 else False if (Result.is_number and Result.is_finite and Result.is_zero is False) else None
print(Result, Answer, sep='\n')

difference	`Abs(log(cos(x))) - log(1 / cos(x))`	→	`-log(1/cos(x)) + Abs(log(cos(x)))`
refine	`refine(Residual, Assum)`	→	`-log(1/cos(x)) + Abs(log(cos(x)))`
answer			`null`

always-none no verdict null 0.0 2026-10-13 16:39:28 3ba0dfac4bca (real x) ∧ (< (abs x) (/ pi 2)) ∧ (nonzero (cos x)) ∧ (nonzero (/ (cos x))) ⊢ (= (abs (log (cos x))) (log (/ (cos x)))) null

sympy-ask no verdict null difference → -log(1/cos(x)) + Abs(log(cos(x))) · ask → None 0.556 2026-10-13 16:39:28 3ba0dfac4bca Q.real(x) ∧ (Abs(x) < (pi/2)) ∧ (~Q.zero(cos(x))) ∧ (~Q.zero((1/cos(x)))) ⊢ Eq(Abs(log(cos(x))), log((1/cos(x)))) null

code

setup — not timed

from sympy import *
import sympy

SympyVersion = sympy.__version__
# warm-up: a fixed generic expression, never case content
W = Symbol('W')
Warmup = ask(Q.positive(W**2 + 1), Q.real(W))
# every query then runs in its own forked process, starting from this state:
# the expression caches are dropped (imported and lazily loaded modules stay)
sympy.core.cache.clear_cache()

x = Symbol('x', real=True)
Assum = And(Q.real(x), Abs(x) < pi / 2, ~Q.zero(cos(x)), ~Q.zero(1 / cos(x)))
Residual = Abs(log(cos(x))) - log(1 / cos(x))
# not Q.eq: in SymPy 1.14 ask(Q.eq(x**2, x), Q.real(x)) is wrongly False
Answer = ask(Q.zero(Residual), Assum)
print(Residual, Answer, sep='\n')

difference	`Abs(log(cos(x))) - log(1 / cos(x))`	→	`-log(1/cos(x)) + Abs(log(cos(x)))`
ask	`Q.zero(Residual)`	→	`None`
answer			`null`

wolfram-fullsimplify solved true difference → Abs[Log[Cos[x]]] - Log[Sec[x]] · result → 0 0.149 2026-10-12 21:55:24 ee702ae2fe06 Element[x, Reals] ∧ (Abs[x] < (Pi/2)) ∧ (Cos[x] != 0) ∧ ((1/Cos[x]) != 0) ⊢ (Abs[Log[Cos[x]]] == Log[(1/Cos[x])]) true

code

setup — not timed

(
  $HistoryLength = 0;
  $Messages = {};
  Warmup = FullSimplify[Sin[W]^2 + Cos[W]^2, Element[W, Reals]];
  GenericWarmup = Quiet[{Simplify[Abs[W] + W, W < 0], Simplify[Sqrt[W^2] - W, W > 0], Refine[Sqrt[W^2], W > 0], Simplify[Log[W V] - Log[W] - Log[V], W > 0 && V > 0], Simplify[Log[-W] - Log[W] - I Pi, W < 0], Simplify[(-1)^(2 W) - 1, Element[W, Integers]], Simplify[Mod[W + 1, 2], Element[W, Integers] && Element[(W - 1)/2, Integers]], Simplify[ArcTan[W] + ArcTan[1/W] - Pi/2, W > 0], FullSimplify[ArcCot[W] - ArcTan[1/W], W > 0], Simplify[Abs[Exp[I W]] - 1, Element[W, Reals]], Simplify[Re[W] - (W + Conjugate[W])/2], Simplify[Gamma[W + 1] - W!, Element[W, Integers] && W > 0], Simplify[Floor[W] - W, Element[W, Integers]], Simplify[Sqrt[W] Sqrt[V] - Sqrt[W V], W > 0 && V > 0], Simplify[HeavisideTheta[W] - 1, W > 0], Simplify[2^W 2^V - 2^(W + V), Element[W, Reals] && Element[V, Reals]], Simplify[Sum[V, {V, 1, W}] - W (W + 1)/2, Element[W, Integers] && W > 0]}];
  Quiet[Check[Message[General::argx, "W", 0], Null]];
  {$Version, Warmup, Length[GenericWarmup]}
)

(* evaluated in a forked copy of the setup kernel: TimeConstrained would not fire here (no timer thread), so the parent enforces a hard timeout of 9 s by killing this process *)
(
  Assum = (Element[x, Reals]) && ((Abs[x] < (Pi/2))) && ((Cos[x] != 0)) && (((1/Cos[x]) != 0));
  Residual = (Abs[Log[Cos[x]]]) - (Log[1/Cos[x]]);
  Result = FullSimplify[Residual, Assum];
  Answer = Which[Result === 0, True, NumericQ[Result] && TrueQ[Result != 0], False, True, Null];
  {Residual, Result, Answer}
)

difference	`(Abs[Log[Cos[x]]]) - (Log[1/Cos[x]])`	→	`Abs[Log[Cos[x]]] - Log[Sec[x]]`
result	`FullSimplify[Residual, Assum]`	→	`0`
answer			`true`

wolfram-refine no verdict null difference → Abs[Log[Cos[x]]] - Log[Sec[x]] · result → -Log[Cos[x]] - Log[Sec[x]] 0.037 2026-10-12 21:55:14 ee702ae2fe06 Element[x, Reals] ∧ (Abs[x] < (Pi/2)) ∧ (Cos[x] != 0) ∧ ((1/Cos[x]) != 0) ⊢ (Abs[Log[Cos[x]]] == Log[(1/Cos[x])]) null

code

setup — not timed

(
  $HistoryLength = 0;
  $Messages = {};
  Warmup = Refine[Sin[W]^2 + Cos[W]^2, Element[W, Reals]];
  GenericWarmup = Quiet[{Simplify[Abs[W] + W, W < 0], Simplify[Sqrt[W^2] - W, W > 0], Refine[Sqrt[W^2], W > 0], Simplify[Log[W V] - Log[W] - Log[V], W > 0 && V > 0], Simplify[Log[-W] - Log[W] - I Pi, W < 0], Simplify[(-1)^(2 W) - 1, Element[W, Integers]], Simplify[Mod[W + 1, 2], Element[W, Integers] && Element[(W - 1)/2, Integers]], Simplify[ArcTan[W] + ArcTan[1/W] - Pi/2, W > 0], FullSimplify[ArcCot[W] - ArcTan[1/W], W > 0], Simplify[Abs[Exp[I W]] - 1, Element[W, Reals]], Simplify[Re[W] - (W + Conjugate[W])/2], Simplify[Gamma[W + 1] - W!, Element[W, Integers] && W > 0], Simplify[Floor[W] - W, Element[W, Integers]], Simplify[Sqrt[W] Sqrt[V] - Sqrt[W V], W > 0 && V > 0], Simplify[HeavisideTheta[W] - 1, W > 0], Simplify[2^W 2^V - 2^(W + V), Element[W, Reals] && Element[V, Reals]], Simplify[Sum[V, {V, 1, W}] - W (W + 1)/2, Element[W, Integers] && W > 0]}];
  Quiet[Check[Message[General::argx, "W", 0], Null]];
  {$Version, Warmup, Length[GenericWarmup]}
)

(* evaluated in a forked copy of the setup kernel: TimeConstrained would not fire here (no timer thread), so the parent enforces a hard timeout of 9 s by killing this process *)
(
  Assum = (Element[x, Reals]) && ((Abs[x] < (Pi/2))) && ((Cos[x] != 0)) && (((1/Cos[x]) != 0));
  Residual = (Abs[Log[Cos[x]]]) - (Log[1/Cos[x]]);
  Result = Refine[Residual, Assum];
  Answer = Which[Result === 0, True, NumericQ[Result] && TrueQ[Result != 0], False, True, Null];
  {Residual, Result, Answer}
)

difference	`(Abs[Log[Cos[x]]]) - (Log[1/Cos[x]])`	→	`Abs[Log[Cos[x]]] - Log[Sec[x]]`
result	`Refine[Residual, Assum]`	→	`-Log[Cos[x]] - Log[Sec[x]]`
answer			`null`

always-none no verdict null 0.0 2026-10-12 21:55:00 ee702ae2fe06 (real x) ∧ (< (abs x) (/ pi 2)) ∧ (nonzero (cos x)) ∧ (nonzero (/ (cos x))) ⊢ (= (abs (log (cos x))) (log (/ (cos x)))) null

wolfram-simplify no verdict null difference → Abs[Log[Cos[x]]] - Log[Sec[x]] · result → Abs[Log[Cos[x]]] - Log[Sec[x]] 0.251 2026-10-12 21:55:00 ee702ae2fe06 Element[x, Reals] ∧ (Abs[x] < (Pi/2)) ∧ (Cos[x] != 0) ∧ ((1/Cos[x]) != 0) ⊢ (Abs[Log[Cos[x]]] == Log[(1/Cos[x])]) null

code

setup — not timed

(
  $HistoryLength = 0;
  $Messages = {};
  Warmup = Simplify[Sin[W]^2 + Cos[W]^2, Element[W, Reals]];
  GenericWarmup = Quiet[{Simplify[Abs[W] + W, W < 0], Simplify[Sqrt[W^2] - W, W > 0], Refine[Sqrt[W^2], W > 0], Simplify[Log[W V] - Log[W] - Log[V], W > 0 && V > 0], Simplify[Log[-W] - Log[W] - I Pi, W < 0], Simplify[(-1)^(2 W) - 1, Element[W, Integers]], Simplify[Mod[W + 1, 2], Element[W, Integers] && Element[(W - 1)/2, Integers]], Simplify[ArcTan[W] + ArcTan[1/W] - Pi/2, W > 0], FullSimplify[ArcCot[W] - ArcTan[1/W], W > 0], Simplify[Abs[Exp[I W]] - 1, Element[W, Reals]], Simplify[Re[W] - (W + Conjugate[W])/2], Simplify[Gamma[W + 1] - W!, Element[W, Integers] && W > 0], Simplify[Floor[W] - W, Element[W, Integers]], Simplify[Sqrt[W] Sqrt[V] - Sqrt[W V], W > 0 && V > 0], Simplify[HeavisideTheta[W] - 1, W > 0], Simplify[2^W 2^V - 2^(W + V), Element[W, Reals] && Element[V, Reals]], Simplify[Sum[V, {V, 1, W}] - W (W + 1)/2, Element[W, Integers] && W > 0]}];
  Quiet[Check[Message[General::argx, "W", 0], Null]];
  {$Version, Warmup, Length[GenericWarmup]}
)

(* evaluated in a forked copy of the setup kernel: TimeConstrained would not fire here (no timer thread), so the parent enforces a hard timeout of 9 s by killing this process *)
(
  Assum = (Element[x, Reals]) && ((Abs[x] < (Pi/2))) && ((Cos[x] != 0)) && (((1/Cos[x]) != 0));
  Residual = (Abs[Log[Cos[x]]]) - (Log[1/Cos[x]]);
  Result = Simplify[Residual, Assum];
  Answer = Which[Result === 0, True, NumericQ[Result] && TrueQ[Result != 0], False, True, Null];
  {Residual, Result, Answer}
)

difference	`(Abs[Log[Cos[x]]]) - (Log[1/Cos[x]])`	→	`Abs[Log[Cos[x]]] - Log[Sec[x]]`
result	`Simplify[Residual, Assum]`	→	`Abs[Log[Cos[x]]] - Log[Sec[x]]`
answer			`null`

Source (conditional.sexp)

(case sp-acj4-130-cond (category simplipy-conditional)
  (note "SimpliPy acj-4 (MIT) rules_real.json[130]: abs log cos _0  ->  log inv cos _0  [weakest assumption found: abs-lt-pi2]")
  (var x real)
  (assume (< (abs x) (/ pi 2)))
  (assume (nonzero (cos x)))
  (assume (nonzero (/ (cos x))))
  (ask (= (abs (log (cos x))) (log (/ (cos x)))))
  (expect true)
  (lean-proof "obtain ⟨r, rfl⟩ := AE.IsReal.exists hd0; have hr : |r| < Real.pi / 2 := (by simpa [AE.abs_ofReal, div_eq_mul_inv] using h0.2); have hr' := abs_lt.mp hr; have hc : 0 < Real.cos r := Real.cos_pos_of_mem_Ioo ⟨hr'.1, hr'.2⟩; refine ⟨by simp; rw [← Complex.ofReal_cos]; exact_mod_cast hc.ne', ?_⟩; rw [AE.cos_ofReal, AE.log_ofReal hc.le, AE.abs_ofReal, AE.inv_ofReal, AE.log_ofReal (inv_nonneg.mpr hc.le), Real.log_inv, abs_of_nonpos (Real.log_nonpos hc.le (Real.cos_le_one r))]"))