Derivative of \( \displaystyle \frac{\ln{\left(1 - x^{2} \right)}}{2} - \frac{\ln{\left(x^{2} + 1 \right)}}{2} \)
Problem 2.1201 · hard
Differentiate \( \displaystyle f(x) = \frac{\ln{\left(1 - x^{2} \right)} - \ln{\left(x^{2} + 1 \right)}}{2} \).
- \[ \frac{d}{d x} \left(\frac{\ln{\left(1 - x^{2} \right)}}{2} - \frac{\ln{\left(x^{2} + 1 \right)}}{2}\right) \]Start with the derivative of the function.✓ Proved
- \[ = \frac{\frac{d}{d x} \left(\ln{\left(1 - x^{2} \right)} - \ln{\left(x^{2} + 1 \right)}\right)}{2} \]constant-multiplePull out the constant factor 1/2.✓ Proved
- \[ = \frac{\frac{d}{d x} \ln{\left(1 - x^{2} \right)}}{2} - \frac{\frac{d}{d x} \ln{\left(x^{2} + 1 \right)}}{2} \]sumApply the difference rule.✓ Proved
- \[ = \frac{\frac{d}{d x} \ln{\left(1 - x^{2} \right)}}{2} + \frac{\frac{d}{d x} \left(- \ln{\left(x^{2} + 1 \right)}\right)}{2} \]algebraDistribute the negative sign.✓ Proved
- \[ = \frac{\frac{d}{d x} \ln{\left(1 - x^{2} \right)}}{2} - \frac{\frac{d}{d x} \ln{\left(x^{2} + 1 \right)}}{2} \]algebraRevert to the standard subtraction form.✓ Proved
- \[ = \frac{\frac{d}{d x} \ln{\left(1 - x^{2} \right)}}{2} - \frac{\frac{d}{d x} \left(x^{2} + 1\right)}{2 \left(x^{2} + 1\right)} \]chainApply the chain rule to the second term.✓ Proved
- \[ = - \frac{\frac{d}{d x} \left(x^{2} + 1\right)}{2 \left(x^{2} + 1\right)} + \frac{\frac{d}{d x} \left(1 - x^{2}\right)}{2 \left(1 - x^{2}\right)} \]chainApply the chain rule to the first term.✓ Proved
- \[ = - \frac{x}{x^{2} + 1} - \frac{x}{1 - x^{2}} \]derivative algebra constant-multipleDifferentiate the inner functions. Simplify the terms. Distribute the 1/2.✓ Proved
- \[ = - \frac{x}{x^{2} + 1} + \frac{x}{x^{2} - 1} \]algebraSimplify the first fraction by multiplying numerator and denominator by -1.✓ Proved
- \[ = \frac{- x \left(x^{2} - 1\right) + x \left(x^{2} + 1\right)}{\left(x^{2} - 1\right) \left(x^{2} + 1\right)} \]algebraFind a common denominator.✓ Proved
- \[ = \frac{2 x}{x^{4} - 1} \]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
| Line | Status | Checked by | Detail |
|---|---|---|---|
| 1 | ✓ Proved | sympy 1.14.0 | line 1 is the problem as stated |
| 2 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where x**2 + 1 = 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(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 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x**2 + 1 = 0 undefined where 1 - x**2 = 0 |
| 9 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 1 - x**2 = 0 undefined where x**2 + 1 = 0 |
| 10 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 1 - x**2 = 0 undefined where x**2 + 1 = 0 |
| 11 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 1 - x**2 = 0 undefined where x**2 + 1 = 0 undefined where x**2 - 1 = 0 |
| 12 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x**2 - 1 = 0 undefined where x**2 + 1 = 0 |
| 13 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x**2 - 1 = 0 undefined where x**2 + 1 = 0 undefined where x**4 - 1 = 0 |
| 14 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x**4 - 1 = 0 |
| answer | ✓ Proved | sympy 1.14.0 | final line against the stated answer: simplify(a - b) reduced to 0 undefined where x**4 - 1 = 0 |
| answer, a second way | ✓ Proved | sympy 1.14.0 | SymPy differentiated f directly and got the stated answer |
Reviewers
gpt-oss:20b: passqwen3.6:27b-mlx: pass
Every verdict on record (4)
qwen3.6:27b-mlx: pass 2026-09-29gpt-oss:20b: pass 2026-09-29qwen3.6:27b-mlx: pass 2026-09-29gpt-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.