JEE Advanced2014MathematicsTrigonometric EquationsActual
For x ϵ 0 , π , the equation sin ⁡ x + 2 sin ⁡ 2 x - sin ⁡ 3 x = 3 has
Options
- AInfinitely solution
- BThree solutions
- COne solution
- DNo solution
Correct answer
D. No solution
Step-by-step solution
sin x + 2 sin 2 x - sin 3 x = 3 sin x + 4 sin x cos x - 3 sin x + 4 sin 3 x = 3 sin x - 2 + 4 cos x + 4 1 - cos 2 x = 3 sin x 2 - 4 cos 2 x - 4 cos x + 1 + 1 = 3 sin x 3 - 2 cos x - 1 2 = 3 ⇒ sin x = 1 a n d 2 cos x - 1 = 0 ⇒ x = π 2 a n d x = π 3 Which is not possible at same time Hence, no solution