buktikan, tolong dijawab

aturan seperti ini
a/b + c/d = (a×d + b×c)/(b×d)
langsung saja soal tidak ditulis lagi

= {(sin x - sin y)(sin x + sin y) + (cos x + cos y)(cos x - cos y)} / {(cos x + cos y)(sin x + sin y)}
= {(sin²x - sin²y) + (cos²x - cos²y)} / {(cos x + cos y)(sin x + sin y)}
= (sin²x + cos²x - sin²y - cos²y) / {(cos x + cos y)(sin x + sin y)}
= (sin²x + cos²x - (sin²y + sin²y)) / {(cos x + cos y)(sin x + sin y)}
= (1 - 1) / {(cos x + cos y)(sin x + sin y)}
= 0 / {(cos x + cos y)(sin x + sin y)}
= 0
jadi 0 dibagi sesuatu hasinya 0