If `costheta = 1/2(a+1/a)` then show that `cos3theta = 1/2(a^3+1/(a^3))`

If costheta= 1/2(a+1/a), show that cos2theta = 1/2*(a^2 + 1/(a^2))

If costheta=1/2(a+1/a), show that : cos3theta=1/2(a^3+1/a^3)

If costheta=1/2(a+1/a) ,show that cos2theta=1/2(a^2+1/a^2)

If costheta=1/2(a+1/a) , then the value of cos 3theta is

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 cos theta = (1)/(2)(a + (1)/(a)), show that cos 30 = (1)/(2) (a^(3) + (1)/(a^(3))) .

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

If sintheta=1/2 , show that (3costheta - 4cos^3theta)=0