cos^3(x)+sin^4(x)-cos^2(x)-sin^2(x)=0
cos^2(x)*(cosx-1)-sin^2(x)*(1-sin^2(x))=0
cos^2(x)*(cosx -1) -cos^2(x)*sin^2(x)
cos^2(x)*(cosx-1-sin^2(x))=0
cos^2(x)*(cos^2(x)+cos(x)-2)=0
cos^2(x)*(cos(x)-1)*(cos(x)+2)=0
1)cos^2(x)=0
cosx=0
x=pi/2+pi*n;
2)
cosx=1
x=2*p*n;
3) cos(x)=-2<-1 решений нет.