Question

Find all solutions in the interval [0, 2π).

cos2x + 2 cos x + 1 = 0

Answer 1

is it cos(2x) or cos^2 x ?

Answer 2

Second choice lol

Answer 3

say cosx = u
u^2 + 2u +1 =0
(u+1)(u+1)=0
root : u = -1
cosx = -1
when x = pi
root = pi

Answer 4

\[x = \pi \]

Answer 5

x = 2π

x = π

x = pi divided by four., seven pi divided by four.

x = pi divided by two., three pi divided by two.

Answer 6

x = pi