Question

преобразуйте произведение в сумму

sin 32° sin58°

sin3х cos9x

Answer 1

1)sin32°•sin58°=1/2(cos(42°-58°)-
cos(32°+58°))=1/2(cos16°-cos90°)=
1/2*cos16°=(cos16°)/2
2)sin3x•cos9x=1/2(sin12x+sin(3x-9x))
=1/2(sin12x-sin6x)