Derivative of \( \displaystyle \frac{\sin{\left(x \right)}}{x + 1} \)
Problem 2.316 · hard
Differentiate \( \displaystyle f(x) = \frac{\sin{\left(x \right)}}{x + 1} \).
- \[ \frac{d}{d x} \frac{\sin{\left(x \right)}}{x + 1} \]derivative rewriteStart with the derivative of the function. Rewrite the denominator using a negative exponent.✓ Proved
- \[ = \sin{\left(x \right)} \frac{d}{d x} \frac{1}{x + 1} + \frac{\frac{d}{d x} \sin{\left(x \right)}}{x + 1} \]productApply the product rule.✓ Proved
- \[ = \sin{\left(x \right)} \frac{d}{d x} \frac{1}{x + 1} + \frac{\cos{\left(x \right)}}{x + 1} \]trigDifferentiate the sine function.✓ Proved
- \[ = \frac{\cos{\left(x \right)}}{x + 1} - \frac{\sin{\left(x \right)} \frac{d}{d x} \left(x + 1\right)}{\left(x + 1\right)^{2}} \]chainApply the chain rule to the power term.✓ Proved
- \[ = \frac{\cos{\left(x \right)}}{x + 1} - \frac{\sin{\left(x \right)}}{\left(x + 1\right)^{2}} \]derivative algebraDifferentiate the inner function x + 1. Simplify the expression by distributing the terms.✓ Proved
- \[ = \frac{x \cos{\left(x \right)} - \sin{\left(x \right)} + \cos{\left(x \right)}}{\left(x + 1\right)^{2}} \]algebraCombine the terms over a common denominator.✓ Proved
- \[ = \frac{\left(x + 1\right) \cos{\left(x \right)} - \sin{\left(x \right)}}{\left(x + 1\right)^{2}} \]simplifySimplify the numerator.✓ Proved
Answer \( \frac{\cos{\left(x \right)}}{x + 1} - \frac{\sin{\left(x \right)}}{\left(x + 1\right)^{2}} \)
✓ 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 undefined where x + 1 = 0 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x + 1 = 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x + 1 = 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x + 1 = 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x + 1 = 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x + 1 = 0 |
| 8 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x + 1 = 0 |
| 9 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x + 1 = 0 |
| answer | ✓ Proved | sympy 1.14.0 | final line against the stated answer: simplify(a - b) reduced to 0 undefined where x + 1 = 0 |
| answer, a second way | ✓ Proved | sympy 1.14.0 | SymPy differentiated f directly and got the stated answer |
Reviewers
gpt-oss:20b: passdeepseek-r1:70b: passqwen3.6:27b-mlx: pass
Every verdict on record (12)
qwen3.6:27b-mlx: pass 2026-09-20gpt-oss:20b: pass 2026-09-20qwen3.6:27b-mlx: pass 2026-09-20 — The solution correctly applies the product rule, chain rule, and algebraic simplification steps. Each step changes only one aspect of the expression and uses valid labels from the fixed vocabulary.gpt-oss:20b: pass 2026-09-20qwen3.6:27b-mlx: pass 2026-09-19 — The solution correctly applies the product rule, chain rule, and algebraic simplifications. Each step changes only one aspect of the expression and uses valid labels from the fixed vocabulary.deepseek-r1:70b: pass 2026-09-19gpt-oss:20b: pass 2026-09-19qwen3.6:27b-mlx: pass 2026-09-19deepseek-r1:70b: pass 2026-09-19gpt-oss:20b: pass 2026-09-19gpt-oss:20b: pass 2026-09-17deepseek-r1:70b: pass 2026-09-17
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.