Solve the trigonometric equation for .

Answer and explanation

Correct answer: B.

  1. Step 1: Isolate the cosine term: . For , the compound angle lies in the interval .
  2. Step 2: The reference angle is , and cosine is positive in the first and fourth quadrants: or . Dividing by 2 gives or .
Answer
.
Why not the others: The angles omit dividing by 2; the angles correspond to ; the angles fail to find the fourth-quadrant solution.

Practise more Trigonometric Functions, Identities and Equations.

Free questions with an explanation for every one, and full timed Singapore GCE O-Level mock tests.