sin^2t-1/ cos^2t+tgt*ctgt
(1+ctg)^2+(1-ctg)^2
cos^2t-ctg^2t/sin^2t-tg^2t

ответ: (sin^2t-1)/(cos^2t-1) + tgt•ctgt=

=(sin^2t-sin^2t-cos^2t)/(cos^2t-sin^2t-cos^2t)+1=

=(-cos^2t/-sin^2t)  +1=(cos^2t/sin^2t)+1=(cos^2t+sin^2t)/sin^2t=1/sin^2t. Это первое)

2 не смогла).

cos^2t-ctg^2t)/(sin^2t-tg^2t)

cos^2t-ctg^2t=cos^2t-cos^2t/sin^2t=(cos^2t*sin^2t-cos^2t)/sin^2t=

=(-cos^2t(1-sin^2t))/sin^2t=-cos^4t/sin^2t  

sin^2t-tg^2t=sin^2t-sin^2t/cos^2t=(sin^2t*cos^2t-sin^2t)/cos^2t=

=(-sin^2t(1-cos^2t))/cos^2t=-sin^4t/cos^2t  

-cos^4t/sin^2t:(-sin^4t/cos^2t)=cos^6t/sin^6t=ctg^6t. Это третье).

Объяснение: