Question

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

Answer 1

$x= \pi$

Step-by-step 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 $\pi (n \pi)$