∫Calc Practice

Derivative of \( \displaystyle \ln{\left(- \cot{\left(3 x \right)} + \csc{\left(3 x \right)} \right)} \)

Problem 2.1828 · hard Beautiful

Differentiate \( \displaystyle f(x) = \ln{\left(- \cot{\left(3 x \right)} + \csc{\left(3 x \right)} \right)} \).
  1. \[ \frac{d}{d x} \ln{\left(- \cot{\left(3 x \right)} + \csc{\left(3 x \right)} \right)} \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = \frac{\frac{d}{d x} \left(- \cot{\left(3 x \right)} + \csc{\left(3 x \right)}\right)}{- \cot{\left(3 x \right)} + \csc{\left(3 x \right)}} \]
    chainApply the chain rule for the natural logarithm.✓ Proved
  3. \[ = \frac{\frac{d}{d x} \left(- \cot{\left(3 x \right)}\right) + \frac{d}{d x} \csc{\left(3 x \right)}}{- \cot{\left(3 x \right)} + \csc{\left(3 x \right)}} \]
    sumApply the sum rule to the derivative of the inner expression.✓ Proved
  4. \[ = \frac{- \frac{d}{d x} \cot{\left(3 x \right)} + \frac{d}{d x} \csc{\left(3 x \right)}}{- \cot{\left(3 x \right)} + \csc{\left(3 x \right)}} \]
    constantFactor out the negative sign from the first term.✓ Proved
  5. \[ = \frac{- 3 \cot{\left(3 x \right)} \csc{\left(3 x \right)} + 3 \csc^{2}{\left(3 x \right)}}{- \cot{\left(3 x \right)} + \csc{\left(3 x \right)}} \]
    trig algebraDifferentiate the trigonometric functions using the chain rule. Simplify the expression by distributing the negative signs.✓ Proved
  6. \[ = 3 \csc{\left(3 x \right)} \]
    algebra simplifyFactor out the common term 3*csc(3*x) from the numerator. Cancel the common factor in the numerator and denominator.✓ Proved
Answer \( \frac{3}{\sin{\left(3 x \right)}} \)
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
log is undefined for non-positive arguments
csc has poles at multiples of pi
cot has poles at multiples of pi
undefined where -cot(3*x) + csc(3*x) = 0
3✓ 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(3*x) + csc(3*x) = 0
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(3*x) + csc(3*x) = 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(3*x) + csc(3*x) = 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(3*x) + csc(3*x) = 0
7✓ 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(3*x) + csc(3*x) = 0
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
csc has poles at multiples of pi
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
undefined where sin(3*x) = 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 (4)
  • qwen3.6:27b-mlx: pass 2026-10-08
  • gpt-oss:20b: pass 2026-10-08
  • gpt-oss:20b: pass 2026-10-08
  • qwen3.6:27b-mlx: pass 2026-10-08

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 2026-10-08 with SymPy 1.14.0.