Question

Перетворити на добуток вираз
Sin7x+sin6x+sin5x

Answer 1

Решение
Sin7x+sin6x+sin5x = (sin7x + sin5x) + sin6x = 
= 2*[sin(7x + 5x)/2 * cos(7x - 5x)/2] + sin6x =
=  2*sin6x * cosx + sin6x = sin6x*(2cosx + 1)