Question

Find all solutions to the equation.

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

Answer 1

(cos(x) +1)(cos(x)+1) = 0

which is true whenever cosx =-1

Answer 2

@Algebraic! can you explain how you did that?

Answer 3

factored cos^2x + 2 cos x + 1

Answer 4

expand (cos(x) +1)(cos(x)+1) and you'll see it's equivalent.

Answer 5

or...
pretend you're factoring u^2 +2u +1
(where u = cos(x) )

Answer 6

@Algebraic! Thank you

Answer 7

sure!