Which set of steps can be used to prove the sine sum identity, sin(x + y) = sin(x)cos(y) + cos(x)sin(y)? Use the complementary relationship between sine and cosine to rewrite sin(x + y) as Cosine (StartFraction pi over 2 EndFraction minus (x + y) ). Apply the cosine sum identity. Then simplify using sin(–y) = –sin(y) and cos(–y) = cos(y). Use the complementary relationship between sine and cosine to rewrite sin(x + y) as Cosine (StartFraction pi over 2 EndFraction minus (x + y) ). Apply the cosine sum identity. Then simplify using sin(–y) = sin(y) and cos(–y) = –cos(y). Use the supplementary relationship between sine and cosine to rewrite sin(x + y) as Cosine (StartFraction pi over 2 EndFraction minus (x + y) ). Apply the cosine sum identity. Then simplify using sin(–y) = –sin(y) and cos(–y) = cos(y). Use the supplementary relationship between sine and cosine to rewrite sin(x + y) as