(1-tg^2a)(1-ctg^2a)==?
sin^2a=1-cos^2a=1-1/9=8/9
tg^2a=sin^2a/cos^2a=8/9:1/9=8/9*9/1=8
ctg^2a=cos^2a/sin^2a=1/9:8/9=1/9*9/8=1/8
=(1-8)(1-1/8)=-7*7/8=-49/8
/дробь
(1-tg^2a)(1-ctg^2a)==?
sin^2a=1-cos^2a=1-1/9=8/9
tg^2a=sin^2a/cos^2a=8/9:1/9=8/9*9/1=8
ctg^2a=cos^2a/sin^2a=1/9:8/9=1/9*9/8=1/8
=(1-8)(1-1/8)=-7*7/8=-49/8
/дробь