If `alpha+beta=gamma`,show that `cos^2alpha+cos^2beta+cos^2gamma=1+2cosalphacosbetacosgamma`

If alpha+beta+gamma=0 ,prove that cosalpha+cosbeta+cosgamma=4cos(alpha/2)cos(beta/2)cos(gamma/2)-1

If secalpha+secbeta+secgamma=0 ,show that (cosalpha+cosbeta+cosgamma)^2=cos^2alpha+cos^2beta+cos^2gamma

If cos(alpha-beta)+cos(beta-gamma)+cos(gamma-alpha)=-3/2 ,show that cosalpha+cosbeta+cosgamma=sinalpha+sinbeta+singamma=0

If tan^2theta=1+2tan^2phi ,show that cos2phi=1+2cos2theta

Prove that cosalpha+cosbeta+cosgamma+cos(alpha+beta+gamma)=4 cos((alpha+beta)/2)cos((beta+gamma)/2)cos((gamma+alpha)/2)

Prove that cos 4A=1-8cos^2A+8 cos^4A

If cos^2alpha-sin^2alpha=tan^2beta ,show that cos^2beta-sin^2beta=tan^2alpha

If tan^2alpha = 1 + tan^2beta ,then prove that cos^2 beta = cot^2alpha

Find cot^2 alpha- cos^2 alpha . .