Question

3sin10x=7cos²5x-sin²5x

Answer 1

3sin10x=7cos²5x-sin²5x

3sin10x = 3sin5x*cos5x

3sin5x*cos5x = 7cos²5x-sin²5x

3sin5x*cos5x= 7cos²5x-(1- cos²5x)

3sin5x*cos5x= 7cos²5x-1+cos²5x

8cos²5x-3sin5x*cos5x-1=0  Делим на cos²5x

8 - 3tg5x - 1 - tg²5x = 0

tg²5x - 3tg5x +7 =0

D<0  -> нет решений