Question

Find all solutions to the equation.
cos^2 x +2cosx+1=0

Answer 1

`x= \pi`

Explanation:

`\cos^2x+\cos x+1=0`

Let
`u= \cos x`

Then
`u^2+2u+1=(u+1)^2=0`

or

`\cos x = -1`

This gives us
`x= \pi` or all integer multiples of
`\pi (n \pi)`