Question

If 2cos theta=x+1/x, then find the value of cos2 theta

Answer 1

Answer:

answer for the given problem is given

Answer 2

FORMULA TO BE USED :-

• cos2theta = 2cos²theta - 1

Given:

• 2costheta = x+1/x

Process:

2costheta = x+1/x

or, costheta = 1/2(x+1/x)

Therefore, cos2theta= 2cos²theta-1

=2{1/2(x+1/x)²} - 1

=1/2(x+1/x)²- 1

=1/2(x²+2+1/x²)-1

=1/2x²+1+1/2×1/x²-1

=1/2(x²+1/x²) [ANS]