Question

7cos(3x+13n/4)=-2 решите прошу !!!

Answer 1

7cos(3x+13π/4)=-2
7cos(3x+8π/4+5π/4)=-2
7cos(3x+2π+5π/4)=-2
7cos(3x+5π/4)=-2
cos(3x+5π/4)=-2/7
3x+5π/4=+-arccos(-2/7)+2πn
3x+5π/4=+-arccos(2/7)+2πn
3x=+-arccos(2/7)-5π/4+2πn
x=+-arccos(2/7)/3-5π/12+2πn/3

Answer 2

В 3 строчке, куда делось 2п?

Answer 3

cos(x)=cos(x+2π)