Hi

Cos^2 (x) + 2cos(x) + 1= 0 

let X  = cos(x)

X^2 + 2X + 1 = 0, X = -1

COS(x) = -1 , x = 180° or any angle 180°  (0 ≤ x ≤ 2pi) 

RELATED QUESTIONS

Solve the equation for x, on the interval 0 is less than or equal to x and 2pi is greater  (answered by Alan3354)

Solve 2cos x+2cos 2x=0 on the interval... (answered by Joker)

1.Solve the equation 2cos x-1=0, 0 (answered by stanbon)

Solve the given equation over the interval [0,2pi): 2cos^2x+cos... (answered by Fombitz)

Solve the equation on the interval [0,360degrees]
cos^2(t)+ 2cos(t)+1=0 help please so... (answered by Cromlix)

Solve the following equation on the interval [0, 2pi]
cos^2 x + 2 cos x + 1 =... (answered by josgarithmetic)

Solve on the interval from 0 to pi:2cos^2 x-3 sin... (answered by lwsshak3)

solve the equation on the interval [0,2π] 
suppose f(x)=2cosθ+1. solve... (answered by tommyt3rd)

solve for 0 (answered by stanbon)