Quadratic in trigHardQuestion 200027
Question
The number of solutions of 2 sin²x + sin x − 1 = 0 in [0, 2π] is:
- A2
- B3Correct
- C4
- D1
Correct answer
3
Explanation
Factor: (2 sin x − 1)(sin x + 1) = 0. So sin x = 1/2 (gives x = π/6, 5π/6) or sin x = −1 (gives x = 3π/2). Total: 3 solutions.