1-cos2a/sin(pi+2a)*tg(pi/2+a)

Question

1-cos2a/sin(pi+2a)*tg(pi/2+a)

Answer 1

(1-сos2a)/sin(π+2a)*tg(π/2+a)=2sin²a/sin2a*(-ctga)=
=2sin²a/(2sinacosa)*(-cosa/sina)=-1