Question

$cos(alpha+frac{pi }{2})cos(3pi-alpha)+sin(alpha +frac{5pi }{2})sin(3pi +alpha)$
$cos(alpha+frac{3pi }{2})cos(alpha-frac{5alpha }{2} )+sin(alpha-3pi)cos(alpha+frac{7pi }{2} )$$cos780, sinfrac{13pi }{6}$$cos(frac{3pi }{2} -alpha), cosalpha =0,8$$sin210 - cos120+ctg225$$tg150+cos780+sin330$$frac{sin(alpha-pi)cos(alpha-2pi )sin(2pi-alpha) }{sin(frac{pi }{2}-alpha)ctg(pi-alpha)ctg(frac{3pi }{2}+alpha ) }$