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

Скобки на месте ставить надо. Скорее всего вид задания таков:(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 - числительsin^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 - знаменательДелим числитель на знаменатель-cos^4t/sin^2t:(-sin^4t/cos^2t)=cos^6t/sin^6t=ctg^6t

(cos²t- cos²t/sin²t)/(sin²t - sin²t/cos²t)=cos²t(sin²t-1)/sin²t : sin²t(cos²t-1)/cos²t==-cos^4t/sin²t :-sin^4t/cos²t=cos^4t/sin²t * cos²t/sin^4t=cos^6t/sin^6t=ctg^6t