NTA Abhyas JEE Main2020MathematicsTrigonometric Ratios & IdentitiesPractice
If x + y = 3 - cos 4 θ and x - y = 4 sin 2 θ , then the value of x + y is equal to
Options
- A2
- B4
- C6
- D8
Correct answer
A. 2
Step-by-step solution
Adding both the given equations, we get, 2 x = 3 + 4 sin ⁡ 2 θ - cos ⁡ 4 θ = 3 + 4 sin ⁡ 2 θ - 1 - 2 sin 2 ⁡ 2 θ = 2 sin 2 ⁡ 2 θ + 4 sin ⁡ 2 θ + 2 ⇒ x = sin 2 ⁡ 2 θ + 2 sin ⁡ 2 θ + 1 ⇒ x = sin ⁡ 2 θ + 1 2 Similarly, 2 y = 3 - cos ⁡ 4 θ - 4 sin ⁡ 2 θ 2 y = 3 - 4 sin ⁡ 2 θ - 1 - 2 sin 2 ⁡ 2 θ = 2 sin 2 ⁡ 2 θ - 4 sin ⁡ 2 θ + 2 ⇒ y = sin 2