cos(7x+pi/4)=-v2/2 7x+pi/4=+-3pi/4 7x1=-pi/4-3pi/4+2pin 7x2=-pi/4+3pi/4+2pin
7x1=-4pi/4+2pin x1=-pi/7+2/7pin 7 x2=2pi/4+2pin x2=pi/14+2pin/7
2ctg(3x+pi/4)-2v3=0 ctg(3x+pi/4)=2v3/2=v3 3x+pi/4=pi/6+pin 3x=-pi/4+pi/6+pin
x=-pi/12+pi/18+pi/3*n=-pi/36+pi/3*n