Question

I have been stuck on this problem for a while and tried different methods but still quite didn't get the answer. Can someone help me? ​

Answer 1

x = 180degrees

Explanation:

Given the expression;

cos²x + 3cosx + 2 = 0

Let P = cosx

P² + 3P + 2 = 0

Factorize

P² + 2p + P + 2 = 0

P(P+2)+(P+2) = 0

(P+2)(P+1) = 0

P = -2 and P = -1

Substitute P = cosx

cos x = -1

x = arccos(-1)

x = 180degrees

Hence the value of x is 180degrees