NTA Abhyas JEE Main2020MathematicsTrigonometric Ratios & IdentitiesPractice
If 0 < α < π 16 and ( 1 + tan α ) 1 + tan 4 α = 2 , then the value of α is equal to
Options
- Aπ 18
- Bπ 20
- Cπ 24
- Dπ 30
Correct answer
B. π 20
Step-by-step solution
We have 1 + tan ⁡ α + tan ⁡ 4 α + tan ⁡ α tan ⁡ 4 α = 2 tan ⁡ α + tan ⁡ 4 α = 1 - tan ⁡ α tan ⁡ 4 α tan ⁡ α + tan ⁡ 4 α 1 - tan ⁡ α tan ⁡ 4 α = 1 tan ⁡ α + 4 α = 1 5 α = π 4 s i n c e ,   0 < α < π 16 Hence, α = π 20