Derivative of \( \displaystyle e^{- 3 x} \sin{\left(3 x \right)} \)
Problem 2.421 · hard
Differentiate \( \displaystyle f(x) = e^{- 3 x} \sin{\left(3 x \right)} \).
- \[ \frac{d}{d x} e^{- 3 x} \sin{\left(3 x \right)} \]derivativeStart with the derivative of the function.✓ Proved
- \[ = \sin{\left(3 x \right)} \frac{d}{d x} e^{- 3 x} + e^{- 3 x} \frac{d}{d x} \sin{\left(3 x \right)} \]productApply the product rule.✓ Proved
- \[ = - 3 e^{- 3 x} \sin{\left(3 x \right)} + e^{- 3 x} \frac{d}{d x} \sin{\left(3 x \right)} \]chainDifferentiate the first part using the chain rule.✓ Proved
- \[ = - 3 e^{- 3 x} \sin{\left(3 x \right)} + 3 e^{- 3 x} \cos{\left(3 x \right)} \]chain algebraDifferentiate the second part using the chain rule. Rearrange the terms.✓ Proved
- \[ = 3 \left(- \sin{\left(3 x \right)} + \cos{\left(3 x \right)}\right) e^{- 3 x} \]simplifyFactor out the common term.✓ Proved
Answer \( \left(- 3 \sin{\left(3 x \right)} + 3 \cos{\left(3 x \right)}\right) e^{- 3 x} \)
✓ 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 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| answer | ✓ Proved | sympy 1.14.0 | final line against the stated answer: simplify(a - b) reduced to 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 — The solution correctly applies the product rule followed by the chain rule for each term. Each step modifies only one part of the expression or applies a single rule, and the labels are accurate.
Every verdict on record (6)
qwen3.6:27b-mlx: pass 2026-09-21 — The solution correctly applies the product rule followed by the chain rule for each term. Each step modifies only one part of the expression or applies a single rule, and the labels are accurate.gpt-oss:20b: pass 2026-09-21qwen3.6:27b-mlx: pass 2026-09-20 — The solution correctly applies the product rule and chain rule in separate steps, adhering to the one-change-per-step constraint. The labels and notes are accurate.gpt-oss:20b: pass 2026-09-20qwen3.6:27b-mlx: pass 2026-09-20gpt-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.