Question

Найдите значение выражения: 1)2-1/sin^2a+ctg^2a

Answer 1

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