Prove that: `cos^2A+cos^2(A+pi/3)+cos^2(A-pi/3)=3/2`

Prove that cos^2x+cos^2(x+pi/3)+cos^2(x-pi/3)=3/2 .

Prove that: cos^2A+cos^2(A+(2pi)/3)+cos^2(A-(2pi)/3)=3/2

Prove that : cos^(2)A+cos^(2)(A+pi/3)+cos^(2)(A-pi/3) = 3/2

Prove any one of the following: cos^2A+cos^2(A+pi/3)+cos^2(A-pi/3)=3/2

Prove that: cos^(2)A+cos^(2)(A+(pi)/(3))+cos^(2)(A-(pi)/(3))=(3)/(2)

Prove that, cos^(2) A + cos^(2) (A + pi/3) + cos^(2) (A - pi/3) = 3/2

Prove that: cos^(2)A+cos^(2)(A+(2 pi)/(3))+cos^(2)(A-(2 pi)/(3))=(3)/(2)

Prove that cos^(2)+x+cos^(2) (x+pi/3)+cos^(2)(x-pi/3)=3/2 and hence find the values of sin^(2)x +sin^(2) (x+pi/3)+sin^(2) (x-pi/3)

Prove that cos^2( pi/8)+cos^2((3pi)/8)+cos^2 ((5pi)/8)+cos^2 ((7pi)/8)=2.

cos^(^^)2A+cos^(^^)2(A+2pi/3)+cos^(^^)2(A-2pi/3)=3/2 OR cos^(^^)2A+cos^(^^)2(A+pi/3)+cos^(^^)2(A-pi/3)=3/2