Prove the identity: simplifies to:

Answer and explanation

Correct answer: C.

  1. Step 1: Expand: .
  2. Step 2: and , so constant is .
  3. Step 3: , bringing sum to .
  4. Step 4: and .
  5. Step 5: Total: .
Answer
.
Why not the others: forgets the terms from and expansions; adds 2 extra units; and option with is not fully simplified.

Practise more Geometry and Trigonometry.

Free questions with an explanation for every one, and full timed CBSE Class 10 mock tests.