Sin^2(t)*cos^2(t)*[(sin^2(t)/cos^2(t))+(cos^2(t)/sin^2(t))+2)]= =sin^2(t)*cos^2(t)*[(sin^4(t)+cos^4(t)+2cos^2(t)*sin^2(t))/sin^2(t)*cos^2(t)]= =(cos^2(t)+sin^2(t))^2=1