If `2costheta=x+1/x`, then `2cos2theta=`?

If 2cos theta=x+1/x then 2cos^2 theta=

If 2 Costheta=x+1/x then 2 cos 3theta=

If 2costheta=x+1/x , prove that 2cos3theta=x^3+1/x^3

If 2costheta=x+(1/x) prove that 2cos3theta=x^3+(1/x^3)

If 2costheta=x+(1)/(x) , then find the value of 2cos^(2)theta .

If 2costheta=x+(1)/(x) then prove that, 2cos3theta=x^(3)+(1)/(x^(3)) .

IF 2 costheta=x+1/x then show that 2 cos3 theta=x^3+1/x^3

i) Prove that: (1-sin2A)/(1+sin2A) = tan^(2)(pi/4-A) ii) If costheta=1/2(x+1/x) , then prove that: cos2theta=1/2(x^(2)+1/x^(2)) and cos3theta=1/2(x^(3)+1/x^(3))

i) Prove that: (1-sin2A)/(1+sin2A) = tan^(2)(pi/4-A) ii) If costheta=1/2(x+1/x) , then prove that: cos2theta=1/2(x^(2)+1/x^(2)) and cos3theta=1/2(x^(3)+1/x^(3))

If 2 cos theta=x+1/x then prove that cos 2 theta=1/2 (x^(2)+1/x^(2))