Question

(sin(3П/2+a)tg(П/2+b))/(cos(П-a)ctg(3П/2-b)) - (sin(3П/2-b)ctg(П/2+a))/(cos(2П-b)tg(П-a))

Answer 1

=(-cosa*(-ctgb))/(-cosa*tgb) - (-cosb*(-tga))/(-cosb*(-tga))=
=-ctgb/tgb  - 1=
=-1-ctg²b=
=-(1+ctg²b)=
=-1/sin²b.