NTA Abhyas JEE Main2020MathematicsTrigonometric Ratios & IdentitiesPractice
If 4 sin 27 o = α - β , then the value of α + β is
Options
- A5
- B3
- C8
- D2
Correct answer
C. 8
Step-by-step solution
cos ⁡ 27 o + sin ⁡ 27 o 2 = 1 + 2 sin ⁡ 27 o cos ⁡ 27 o = 1 + sin ⁡ 54 o = 1 + cos ⁡ 36 o ⇒ cos ⁡ 27 o + sin ⁡ 27 o = 1 + cos ⁡ 36 o Similarly, cos ⁡ 27 o - sin ⁡ 27 o = 1 - cos ⁡ 36 o (since, cos ⁡ 27 o > sin ⁡ 27 o ) On subtracting, we get, 2 sin ⁡ 27 o = 1 + cos ⁡ 36 o - 1 - cos ⁡ 36 o = 1 + 5 + 1 4 - 1 - 5 + 1 4 = 5 + 5 2 - 3 - 5 2 ⇒ 4 sin ⁡ 27 o = 5 + 5 - 3 - 5 ⇒ α = 5 + 5 and