∫Calc Practice
Home›Calculus 1›Product rule›Problem 2.1939

Derivative of \( \displaystyle - \frac{e^{4 x} \sin{\left(4 x \right)}}{8} + \frac{e^{4 x} \cos{\left(4 x \right)}}{8} \)

Problem 2.1939 · hard

Differentiate \( \displaystyle f(x) = - \frac{e^{4 x} \sin{\left(4 x \right)}}{8} + \frac{e^{4 x} \cos{\left(4 x \right)}}{8} \).
  1. \[ \frac{d}{d x} \left(- \frac{e^{4 x} \sin{\left(4 x \right)}}{8} + \frac{e^{4 x} \cos{\left(4 x \right)}}{8}\right) \]
    sumStart with the derivative of the sum.✓ Proved
  2. \[ = \frac{d}{d x} \left(- \frac{e^{4 x} \sin{\left(4 x \right)}}{8}\right) + \frac{d}{d x} \frac{e^{4 x} \cos{\left(4 x \right)}}{8} \]
    constant-multiplePull out the constant factors.✓ Proved
  3. \[ = - \frac{\frac{d}{d x} e^{4 x} \sin{\left(4 x \right)}}{8} + \frac{\frac{d}{d x} e^{4 x} \cos{\left(4 x \right)}}{8} \]
    productApply the product rule to each term.✓ Proved
  4. \[ = - \frac{e^{4 x} \frac{d}{d x} \sin{\left(4 x \right)}}{8} + \frac{e^{4 x} \frac{d}{d x} \cos{\left(4 x \right)}}{8} - \frac{\sin{\left(4 x \right)} \frac{d}{d x} e^{4 x}}{8} + \frac{\cos{\left(4 x \right)} \frac{d}{d x} e^{4 x}}{8} \]
    exponentialDifferentiate the exponential functions.✓ Proved
  5. \[ = - \frac{e^{4 x} \sin{\left(4 x \right)}}{2} + \frac{e^{4 x} \cos{\left(4 x \right)}}{2} - \frac{e^{4 x} \frac{d}{d x} \sin{\left(4 x \right)}}{8} + \frac{e^{4 x} \frac{d}{d x} \cos{\left(4 x \right)}}{8} \]
    trigDifferentiate the trigonometric functions.✓ Proved
  6. \[ = - e^{4 x} \sin{\left(4 x \right)} \]
    algebra simplify algebra simplify simplifyDistribute the constants inside the parentheses. Simplify the coefficients. Combine like terms. Cancel the cosine terms. Combine the remaining sine terms.✓ Proved
Answer \( - e^{4 x} \sin{\left(4 x \right)} \)

✓ 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
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
9✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
10✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 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: fail (style) — Step 2 is labeled 'constant-multiple' but performs the 'sum' rule (splitting the derivative of a sum into a sum of derivatives). Step 3 is labeled 'product' but performs the 'constant-multiple' rule (pulling out the 1/8 factors). The labels are swapped.
Every verdict on record (4)
  • gpt-oss:20b: pass 2026-10-09
  • qwen3.6:27b-mlx: fail (style) 2026-10-09 — Step 2 is labeled 'constant-multiple' but performs the 'sum' rule (splitting the derivative of a sum into a sum of derivatives). Step 3 is labeled 'product' but performs the 'constant-multiple' rule (pulling out the 1/8 factors). The labels are swapped.
  • qwen3.6:27b-mlx: fail (style) 2026-10-09 — Step 2 is labeled 'constant-multiple' but performs the 'sum' rule (splitting the derivative of a sum into a sum of derivatives). Step 3 is labeled 'product' but performs the 'constant-multiple' rule (pulling out the 1/8 factors). The labels are swapped.
  • gpt-oss:20b: fail (style) 2026-10-09 — The solution labels the differentiation of exp(4*x) and sin(4*x) as "exponential" and "trig" respectively, but each of those steps also requires the chain rule (derivative of 4*x). Since only one rule may be named per step, the missing "chain" label is a labeling defect.

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 2026-10-09 with SymPy 1.14.0.