Докажите равенство: cos 48 + sin 18 - cos 12 = 0

Cos 48 = sin 42, cos 12 = sin 78 sin 42 + sin 18= sin 78 formula: sinx + sin y = 2. sin(x+y)/2.cos (a-b)/2 sin 42 + sin 18 = 2.sin 30 .cos 12= 2.1/2.cos 12=cos 12 = sin 78 (sin (90-x) =cos x)