Prove the following:`cos^2x+cos^2(x+120^@)+cos^2(x-120^@)=3/2`

Prove the following: cos(x+y)cos(x-y)=cos^2y-sin^2x

Select and write the correct answer from the given alternatives in each of the following: cos^2theta+cos^2(theta+120^@)+cos^2(theta-120^@) =……….

Prove the following: cos^2 2x-cos^2 6x=sin4xsin8x

Prove the following: 4cosxcos(pi/3+x)cos(pi/3-x)=cos3x

Prove the following: cos(pi/4+x)+cos(pi/4-x)=sqrt2cosx

Prove the following: (cosx+cosy)^2+(sinx-siny)^2=4cos^2(frac(x+y)(2))

Prove the following: (frac(2cos4x+1)(2cosx+1))=(2cosx-1)(2cos2x-1)

Prove the following: cos(3pi/2+x)cos(2pi+x)[cot(3pi/2-x)+cot(2pi+x)]=1

Prove the following: (frac(sin3x)(cosx))+(frac(cos3x)(sinx))=2cot2x

Prove the following: cos(pi/2-x)cos(pi/2-y)-sin(pi/2-x)sin(pi/2-y)=-cos(x+y)