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Derivative of \( \displaystyle \frac{\ln{\left(1 - x^{2} \right)}}{2} - \frac{\ln{\left(x^{2} + 1 \right)}}{2} \)

Problem 2.1201 · hard

Differentiate \( \displaystyle f(x) = \frac{\ln{\left(1 - x^{2} \right)} - \ln{\left(x^{2} + 1 \right)}}{2} \).
  1. \[ \frac{d}{d x} \left(\frac{\ln{\left(1 - x^{2} \right)}}{2} - \frac{\ln{\left(x^{2} + 1 \right)}}{2}\right) \]
    Start with the derivative of the function.✓ Proved
  2. \[ = \frac{\frac{d}{d x} \left(\ln{\left(1 - x^{2} \right)} - \ln{\left(x^{2} + 1 \right)}\right)}{2} \]
    constant-multiplePull out the constant factor 1/2.✓ Proved
  3. \[ = \frac{\frac{d}{d x} \ln{\left(1 - x^{2} \right)}}{2} - \frac{\frac{d}{d x} \ln{\left(x^{2} + 1 \right)}}{2} \]
    sumApply the difference rule.✓ Proved
  4. \[ = \frac{\frac{d}{d x} \ln{\left(1 - x^{2} \right)}}{2} + \frac{\frac{d}{d x} \left(- \ln{\left(x^{2} + 1 \right)}\right)}{2} \]
    algebraDistribute the negative sign.✓ Proved
  5. \[ = \frac{\frac{d}{d x} \ln{\left(1 - x^{2} \right)}}{2} - \frac{\frac{d}{d x} \ln{\left(x^{2} + 1 \right)}}{2} \]
    algebraRevert to the standard subtraction form.✓ Proved
  6. \[ = \frac{\frac{d}{d x} \ln{\left(1 - x^{2} \right)}}{2} - \frac{\frac{d}{d x} \left(x^{2} + 1\right)}{2 \left(x^{2} + 1\right)} \]
    chainApply the chain rule to the second term.✓ Proved
  7. \[ = - \frac{\frac{d}{d x} \left(x^{2} + 1\right)}{2 \left(x^{2} + 1\right)} + \frac{\frac{d}{d x} \left(1 - x^{2}\right)}{2 \left(1 - x^{2}\right)} \]
    chainApply the chain rule to the first term.✓ Proved
  8. \[ = - \frac{x}{x^{2} + 1} - \frac{x}{1 - x^{2}} \]
    derivative algebra constant-multipleDifferentiate the inner functions. Simplify the terms. Distribute the 1/2.✓ Proved
  9. \[ = - \frac{x}{x^{2} + 1} + \frac{x}{x^{2} - 1} \]
    algebraSimplify the first fraction by multiplying numerator and denominator by -1.✓ Proved
  10. \[ = \frac{- x \left(x^{2} - 1\right) + x \left(x^{2} + 1\right)}{\left(x^{2} - 1\right) \left(x^{2} + 1\right)} \]
    algebraFind a common denominator.✓ Proved
  11. \[ = \frac{2 x}{x^{4} - 1} \]
    algebra simplifyExpand the numerator and denominator. Combine like terms in the numerator.✓ Proved
Answer \( \frac{2 x}{x^{4} - 1} \)
Mind the domain. The answer is also defined on (-oo, -1) and (1, oo), 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
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where x**2 + 1 = 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where x**2 + 1 = 0
undefined where 1 - x**2 = 0
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**2 + 1 = 0
undefined where 1 - x**2 = 0
9✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 1 - x**2 = 0
undefined where x**2 + 1 = 0
10✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 1 - x**2 = 0
undefined where x**2 + 1 = 0
11✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 1 - x**2 = 0
undefined where x**2 + 1 = 0
undefined where x**2 - 1 = 0
12✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**2 - 1 = 0
undefined where x**2 + 1 = 0
13✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**2 - 1 = 0
undefined where x**2 + 1 = 0
undefined where x**4 - 1 = 0
14✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**4 - 1 = 0
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
undefined where x**4 - 1 = 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 2026-09-29
  • gpt-oss:20b: pass 2026-09-29
  • qwen3.6:27b-mlx: pass 2026-09-29
  • gpt-oss:20b: pass 2026-09-29

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 2026-09-29 with SymPy 1.14.0.