What is the exact value of ?
Answer and explanation
Correct answer: C.
- Step 1: Evaluate : since sine is an odd function, .
- Step 2: Evaluate : in Quadrant II, cosine is negative: .
- Step 3: Add the terms: .
Answer
.
Why not the others: '' assumes the terms cancel, treating cosine in Quadrant II as positive; '' ignores both negative signs; '' confuses with .
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