44 балла. Упростить (sin^2 a*cos^2 a+sin^4 a) /(sin^2 a cos^2 a + cos^4 a -1)
=(sin^2a(cos^2a+sin^2a))/(sin^2acos^2a+(cos^2a+1)(cos^2a-1))= =sin^2a/(sin^2acos^2a-sin^2a(cos^2a+1))=1/(cos^2a-cos^2a-1)=-1