If `cos alpha+cos beta=0=sin alpha+sinbeta, then cos2alpha+cos 2beta=`

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 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 cosalpha+cosbeta=0=sinalpha+sinbeta, then cos2alpha+cos2beta is equal to (a) -2"sin"(alpha+beta) (b) -2cos(alpha+beta) (c) 2"sin"(alpha+beta) (d) 2"cos"(alpha+beta)

If cosalpha+cosbeta=0=sinalpha+sinbeta, then cos2alpha+cos2beta is equal to (a) -2"sin"(alpha+beta) (b) -2cos(alpha+beta) (c) 2"sin"(alpha+beta) (d) 2"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. Prove that cos2 alpha+cos2 beta=-2cos(alpha+beta)

If cosalpha+cosbeta=0=sinalpha+sinbeta, then prove that cos2alpha+cos2beta=-2cos(alpha+beta) .