sgnhome Sin^4(x)+cos^4(x)-2sin^2(x)cos^2(x)=0
(Sin^2(x)-cos^2(x))^2=0
Sin^2(x)-cos^2(x)=0
Tg^2(x)-1=0
Tg x=1 или tg x=-1
X=П/4+Пn/2