Question

Find all solutions to the equation.

cos2x + 2 cos x + 1 = 0

Answer 1

ambiguous!

Answer 2

Does cos2x mean \[\cos ^{2}x ?\]

Answer 3

Factor the left side.

Answer 4

cos2x = cosx^2 - sinx^2 and 1=sinx^2 + cosx^2.

cancel the sinx^2

and you get 2cosx^2 + 2cosx = 0

set cosx = u and then factor it or use quadratic formula.

Answer 5

@melacho If you want help you MUST clarify:
Is it cos(2x) or cos^2(x) ???

Answer 6

and is there a domain?

Answer 7

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

Answer 8

Then factor the left side. It is like this: x^2+2x+1

Answer 9

notice is just a quadratic, thus you'd solve it like you'd any quadratic

Answer 10

I am so confused >.< I'm sorry

Answer 11

(cosx + 1)^2 = 0

better?

Answer 12

cos(x)+1=0
cos(x)=1
x 3pi/2kpi

Answer 13

cos x = -1
x=pi + 2kpi