If ` cos alpha + cos beta =0 = sin alpha + sin beta " then " cos (alpha - beta )=`

If cos alpha + cos beta =0 = sin alpha + sin beta , then cos 2 alpha + cos 2 beta is equal to

If cos alpha + cos beta = 0 = sin alpha + sin beta, then value of cos 2 alpha + cos 2 beta is

If cos alpha+cos beta=0=sin alpha+sin beta then cos2 alpha+cos2 beta=

If cos alpha+cos beta=0=sin alpha+sin beta , then cos 2 alpha+cos 2beta is equal to

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)

If cos alpha+cos beta=0=sin alpha+sin beta, then cos2 alpha+cos2 beta is equal to

If cos alpha+cos beta=0=sin alpha+sin beta, then cos2 alpha+cos2 beta is equal to (a)-2sin(alpha+beta)(b)-2cos(alpha+beta)(c)2sin(alpha+beta)(d)2cos(alpha+beta)

If cos alpha+cos beta=0=sin alpha+sin beta. Prove that cos2 alpha+cos2 beta=-2cos(alpha+beta)