Question

побратски помогите sin7x-sinx=cos4x

Answer 1

sin7x-sinx=cos4x;⇒
2sin3x·cos4x=cos4x;⇒
2sin3x=1;⇒sin3x=1/2;
3x=(-1)^k·π/6+kπ;k∈Z;x=(-1)^k·π/18+kπ/3;