Find the derivative of y = sin(xe^x) with respect to x.

Source: JAMB · 2024

Find the derivative of y = sin(xe^x) with respect to x.

  1. dy/dx = cos(xe^x)(e^x + xe^x) ✓
  2. dy/dx = -cosec(xe^x)(e^x + xe^x)
  3. dy/dx = cos(xe^x)(xe^x)
  4. dy/dx = sec(xe^x)(e^x + xe^x)
Explanation

Use the chain rule: the derivative of sin(u) is cos(u) × du/dx. Here u = xe^x.

For u, use the product rule: d/dx (x · e^x) = 1 · e^x + x · e^x = e^x + xe^x.

So dy/dx = cos(xe^x)(e^x + xe^x).

The cosec and sec options are wrong because the derivative of sin is cos, with no minus sign.

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