What is the exact value of ?

Answer and explanation

Correct answer: D.

  1. Step 1: Let , which means and .
  2. Step 2: Calculate .
  3. Step 3: Use the double angle identity: .
Answer
.
Why not the others: omits the factor of (); calculates ; is simply .

Practise more Trigonometric functions and inverse trigonometric functions.

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