Упростить выражение (2+cos a) * (2-cos a) + (2-sin a) * (2+sin a)

Упростите выражения

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

(1-2*sin (x) * cos (x)) / (sin (2x) - 1) =

(1-sin (2x)) / (sin (2x) - 1) = - 1

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

(1-sin (a)) (1+sin (a)) / (1+sina) =

2*sin (a) + 2 * (1-sin (a)) = 2