Question

How do you solve `8cos^3x-1=0`?

Answer 1

`pi/3 + 2kpi`
`(5pi)/3 + 2kpi`

Explanation:

`cos^3 x = 1/8`
`cos x = 1/2`
Trig table and unit circle give 2 arcs x that have same cos value.
`cos x = 1/2` --> `x = +- pi/3`
The arc `(-pi/3)` is the same as the arc `(5pi)/3` --> (co-terminal)
General answers:
`x = pi/3 + 2kpi`
`x = (5pi)/3 + 2kpi`