Answer:
Step-by-step explanation:
given the expression;
cos(2x) = cos(x)
According to trig identity;
cos(2x) = cos(x+x)
cos(2x) = cos x cos x - sinx sinx
cos(2x) = cos²(x)-sin²(x)
cos(2x) = cos²(x)-(1-cos²x)
cos(2x) = cos²(x)+cos²x-1
cos(2x) = 2cos²(x)-1
2cos²(x)-1 = cos(x)
let P = cosx
2P²-1 = P
2P²-P-1 = 0
Factorize;
2P²-2P+P-1 = 0
2P(P-1)+1(P-1) = 0
2P - 1 = 0 and P-1 = 0
P = 1/2 and 1
cosx = 1/2 and cos x = 1
x = arccos 1/2
x = π/3
Also;
x = arccos1
x = 0
Hence the value of x are 0 and π/3
Also the angle = π+ π/3 = 4π/3
The angles are 0, π/3 and 4π/3
