If `cosalpha+cosbeta = 0=sinalpha+sinbeta`, then `cos2alpha+cos2beta` is equal to

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

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

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

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

If cosalpha+cosbeta=0=s inalpha+s inbeta, then prove that cos2alpha+cos2beta=-2cos(alpha+beta)dot

(cosalpha+cosbeta)^2+(sinalpha+sinbeta)^2 =

If cosalpha+cosbeta+cosgamma=0=sin alpha+sinbeta+singamma then cos^2alpha+cos^2beta+cos^2gamma=

The expression (sinalpha+sinbeta)/(cosalpha+cosbeta) is equal to