Выражение sin^4x+3 sin^2x cos^4x-sin^2x*cos^2x+3sin^4x*cos^2x+cos^4x

=((sin^2 ))^2 +(cos^2 x)^2) -sin^2 x cos^2 x +3sin^2 x cos^2 x *(cos^2 x +
+sin^2 x)=(sin^2 x)^2 +(cos^2 x)^2 +2sin^2 x cos^2 x=(sin^2 x+cos^2 x)^2=1