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)-cos2 alpha cos2 beta is

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

If the sides of two sides of a right angled triangle are (cos2 alpha+cos2 beta+2cos(alpha+beta)) and (sin2 alpha+sin2 beta+2sin(alpha+beta)) then find the hypotenuse

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 ^ (2) alpha + cos ^ (2) (alpha + beta) -2cos alpha cos beta cos (alpha + beta) = sin ^ (2) beta

Sum the series : (1+cos alpha) +(1+ cos2alpha) +(1+ cos3alpha) +..... to n terms.

If A = cos ^(2) alpha + cos ^2(alpha + beta)- 2 cos alpha cos beta cos (alpha + beta), then

If cos alpha+cos beta=0=sin alpha+sin beta, then prove that cos2 alpha+cos2 beta=-2cos(alpha+beta)

If cos alpha+cos beta=0=sin alpha+sin beta, then prove that cos2 alpha+cos2 beta=-2cos(alpha+beta)