How do i find x?

Question

How do i find x?    

cos2x=0

Answer 1

cos(2x) = 0

 

We know cos is zero at 90 degrees or π/2 and again at 270 degrees or 3π/2

 

This is represented as π/2 ± nπ

 

2x = π/2 ± nπ

 

x = π/4 ± nπ/2 for n = integers (-∞,∞)

Answer 2

Let u = 2x

 

cos(u) = 0 at u = n*pi/2 where n = 0, ±1, ±2, ±3, ...

 

u = 2x = n*pi/2

 

x = n*pi/4, n = 0, ±1, ±2, ±3, ...