Will medal and fan!!
Find all solutions to the equation.

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

Question

Will medal and fan!!
Find all solutions to the equation.

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

kobeni-chan · Answer

@Michele_Laino

hartnn · Answer

could you first find 2 values of cos x ?
its a quadratic in cos x......

hartnn · Answer

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

kobeni-chan · Answer

Sorry I'm confused >_< 
From what they've been teaching me, I'm supposed to isolate the trig. part, and then add 2πn to each solution..?

hartnn · Answer

yes,
all that was just to isolate (or find the multiple values of) the trig part which is cos x here.

since the equation is quadratic in cos x,
it can have multiple values.
hence first find them, then we can proceed.

hartnn · Answer

let y = cos x 
y^2 +2y +1 = 0 

y =...

hence, cos x = ...

kobeni-chan · Answer

Ohh ok. Is it +1 and +1 again? :/ or (y+1)^2

hartnn · Answer

(y+1)^2 = 0 

so y+1 = 0
so, y = -1 

cos x = -1 
for what values does cos give you -1?