Highly selective Backlog Qs for JEE MainMathematicsComplex Number
The expression 1 + i tan α 1 - i tan α n - 1 + i tan n α 1 - i tan n α when simplified reduces to
Options
- Azero
- B2 sin n α
- C2 cos n α
- Dnone
Correct answer
A. zero
Step-by-step solution
Let 1 + i tan α 1 - i tan α n - 1 + i tan n α 1 - i tan n α = z We know that tan α = sin α cos α ⇒ z = cos α + i sin α cos α - i sin α n - cos n α + i sin n α cos n α - i sin n α From Euler formula, we get ⇒ z = e i α e - i α n - e i n α e - i n α ⇒ z = e 2 i α n - e 2 i n α = e 2 i n α - e 2 i n α = 0 ∴ 1 + i tan α 1 - i tan α n - 1 + i tan n α 1 - i tan n α