Find the sum to n terms o the series `cos^2 alpha+cos^2(alpha+beta)+cos^2(alpha+2beta)+..`

Find the sum of the series cosalpha+x cos(alpha+beta)+ x^2/(2!)cos(alpha+2beta)+…to oo

The expression cos^2(alpha+beta)+cos^2(alpha-beta)-cos2alphacos2beta is

Find the sum of the series sin^2alpha+sin^2(alpha+beta)+sin^2(alpha+2beta)…+sin^2(alpha +(n-1) beta)

If cos(alpha+beta)=0 then sin(alpha+2beta)=

Sum of n terms of the series sinalpha-sin(alpha+beta)+sin(alpha+2beta)-sin(alpha+3beta)+….

Sum of n terms of the series sinalpha-sin(alpha+beta)+sin(alpha+2beta)-sin(alpha+3beta)+….

Sum the series cosalpha+^nC_1 cos(alpha+beta)+^nC_2 cos (alpha+2beta)+…+cos(alpha+nbeta)

If the sides of a right angled triangle are {cos 2 alpha + cos 2 beta + 2 cos (alpha+beta)} and {sin 2 alpha+sin 2 beta + 2 sin (alpha+beta)} then the length of the hypotneuse is

Prove that : cos^2alpha+cos^2(alpha+beta)-2cosalphacosbetacos(alpha+beta)=sin^2beta

If alpha+beta= 60^0 , prove that cos^2 alpha + cos^2 beta - cosalpha cos beta = 3/4 .