Г)=4/sin^2a-4cos^2a/sin^2a=4-4cos^2/sin^2a=4(1-cos^2a)/sin^2a=4(sin^2a+cos^2a-cos^2a)/sin^2a=4sin^2a/sin^2a=4
B)=cos^2a-sin^2a- cos^2a/3(1-sin^2a)=-sin^2a/3(sin^2a+cos^2a-sin^2a)=-sin^2a/3cis^2a=-tg^2a/3
Б)=2sin^2a-sin^2a-cos2a/sin^2a+сos^2a-2cos^2a=sin^2a-cos^2a/sin^2a-cos^2a=1
P.s ^2-- во второй степени)