If , what is ?
Answer and explanation
Correct answer: B.
- Step 1: Use the chain rule: , so .
- Step 2: Compute the inner derivative: .
- Step 3: Combine terms: .
- Step 4: Use the double-angle identity with : .
Answer
.
Why not the others: '' drops the cosine factor; '' is the unsimplified form but the option provides the equivalent trigonometric identity form; '' omits the chain rule factor of 3 from .
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