Question

Упростить:
4 sin 80° *sin 10°

Answer 1

$sin alpha +sin beta=2sin frac{ alpha + beta }{2}cosfrac{ alpha - beta }{2} \ left { {{ frac{ alpha + beta }{2}=80} atop frac{ alpha - beta }{2}=10}} right\ left { {{ alpha =90} atop { beta=70}} right. \ 4sin80sin10=2(sin90+sin70)=2+2sin70$