Упростить. 1) (1/sin^2a) - (ctg^2a) - (cos^2b) 2) (ctg^2a-cos^2a) * ((1/1cos^2a) - 1)

Приведем к общему знаменателю и сократим дроби:

1) x = 1/sin^2 (a) - ctg^2 (a) - cos^2 (b);

x = 1/sin^2 (a) - cos^2 (a) / sin^2 (a) - cos^2 (b); x = (1 - cos^2 (a)) / sin^2 (a) - cos^2 (b); x = sin^2 (a) / sin^2 (a) - cos^2 (b); x = 1 - cos^2 (b); x = sin^2 (b).

2) y = (ctg^2 (a) - cos^2 (a)) * (1/cos^2 (a) - 1);

y = (cos^2 (a) / sin^2 (a) - cos^2 (a)) * (1 - cos^2 (a)) / cos^2 (a); y = cos^2 (a) (1/sin^2 (a) - 1) * sin^2 (a) / cos^2 (a); y = (1/sin^2 (a) - 1) * sin^2 (a); y = 1 - sin^2 (a); y = cos^2 (a).

Ответ: 1) sin^2 (b); 2) cos^2 (a).