Sin^2 j cos^2 j/(1-sin^6 j-cos^6 j)=1/3
1) преобразуем знаменатель:
1 - sin^6j- cos^6j=sin^2j+cos^2j-sin^6j-cos^6j=
=sin^2j(1-sin^4j)+cos^2j(1-cos^4j)=
=sin^2j(1-sin^2j)(1+sin^2j)+
+cos^2j(1-cos^2j)(1+cos^2j)=
=sin^2jcos^2j(1+sin^2j)+cos^2jsin^2j(1+cos^2j)=
=sin^2jcos^2j(1+sin^2j+1+cos^2j)=
=3sin^2jcos^2j;
2) sin^2jcos^2j/3sin^2jcos^2j=1/3.