Verify the trig identity by working on the left side only. Work vertically. Verify the trig identity by working on the left side only. Work vertically. (1 - cost )(1 + cos ) = 1/cosc2 cos + sin tan = sec Solution A)(1-cosv)*(1+cosv)=1-cos2v=sin2v=1/cosec2v as cos2v+sin2v B)cosv+sinv*tanv=cosv+sin2v/cosv=cos2v+sin2v/cosv=1/cosv=secv,as cos2v+sin2v=1.