Question

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

Answer 1

$Sin(frac{pi }{2}+alpha)+Cos(pi+alpha)+tg(frac{3pi }{2}-alpha)+Ctg(2pi -alpha )=Cosalpha-Cosalpha+Ctgalpha-Ctgalpha=0$