sinA−sinBcosA+cosB+cosA−cosBsinA+sinB=
0
sinA−sinBcosA+cosB+cosA−cosBsinA+sinB
= (sinA−sinB)(sinA+sinB) + (cosA−cosB)(cosA+cosB)(cosA+cosB)(sinA+sinB)
=sin2A−sin2B+cos2A−cos2B(cosA + cosB)(sinA + sinB)
= sin2A + cos2A − (sin2B ‘+ cos2B)(cosA + cosB)(sinA + sinB)
= 1−1(cosA + cosB)(sinA + sinB)
= 0