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Derivative of \( \displaystyle \operatorname{atan}{\left(\cot{\left(2 x - 1 \right)} \right)} \)

Problem 2.535 · hard Beautiful

Differentiate \( \displaystyle f(x) = \operatorname{atan}{\left(\cot{\left(2 x - 1 \right)} \right)} \).
  1. \[ \frac{d}{d x} \operatorname{atan}{\left(\cot{\left(2 x - 1 \right)} \right)} \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = \frac{\frac{d}{d x} \cot{\left(2 x - 1 \right)}}{\cot^{2}{\left(2 x - 1 \right)} + 1} \]
    chainApply the chain rule to the arctangent function.✓ Proved
  3. \[ = - \frac{\csc^{2}{\left(2 x - 1 \right)} \frac{d}{d x} \left(2 x - 1\right)}{\cot^{2}{\left(2 x - 1 \right)} + 1} \]
    chainApply the chain rule to the cotangent function.✓ Proved
  4. \[ = - \frac{2 \csc^{2}{\left(2 x - 1 \right)}}{\cot^{2}{\left(2 x - 1 \right)} + 1} \]
    derivative algebraDifferentiate the innermost linear function. Multiply the terms together.✓ Proved
  5. \[ = -2 \]
    algebra simplifyUse the identity 1 + cot(u)**2 = csc(u)**2. Simplify the resulting expression.✓ Proved
Answer \( -2 \)
Mind the domain. The answer is also defined at points where f(x) is not. Substituting there gives a number that is not a slope of f.

✓ Nihil obstat Every line of this solution was proved by the computer algebra system SymPy. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation.

The full receipt
LineStatusChecked byDetail
1✓ Provedsympy 1.14.0line 1 is the problem as stated
2✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
cot has poles at multiples of pi
undefined where cot(2*x - 1)**2 + 1 = 0
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
cot has poles at multiples of pi
undefined where cot(2*x - 1)**2 + 1 = 0
csc has poles at multiples of pi
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
csc has poles at multiples of pi
cot has poles at multiples of pi
undefined where cot(2*x - 1)**2 + 1 = 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
csc has poles at multiples of pi
cot has poles at multiples of pi
undefined where cot(2*x - 1)**2 + 1 = 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
csc has poles at multiples of pi
cot has poles at multiples of pi
undefined where cot(2*x - 1)**2 + 1 = 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
answer, a second way✓ Provedsympy 1.14.0SymPy differentiated f directly and got the stated answer

Reviewers

  • gpt-oss:20b: pass
  • qwen3.6:27b-mlx: pass
Every verdict on record (6)
  • qwen3.6:27b-mlx: pass 2026-09-21
  • gpt-oss:20b: pass 2026-09-21
  • qwen3.6:27b-mlx: pass 2026-09-20
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-20
  • gpt-oss:20b: pass 2026-09-20

Proved: SymPy reduced the difference between the two sides to zero. Checked independently: a separate method, named above, confirmed it. Checked numerically: the two sides agree at every sampled point, which is evidence, not proof. Reviewed: a model or a person read it; that is all a sentence can have. Solution by gemma4:26b, checked 2026-09-26 with SymPy 1.14.0.