Question

When cosx=0, what does x equal?

Answer 1

`90^o`

Explanation:

`x=` `cos^-1(0)` = `90^o`

Using the cosine graph,

`x` could also `= 270^o, 450^o, 810^o, -90^o, -270^o, -450^o, -810^o` etc.

Answer 2

`+- pi/2`

Explanation:

Trig unit circle -->
cos x = 0 --> arc `x = +- pi/2`
For period (0, 2pi), the answers are:
`pi/2 and (3pi)/2`
Note. The arc -`(pi/2)` is co-terminal to the arc `(3pi)/2`