sin(π/2-β)cos(a+β)-sin(a+β)sin(2π-β)=cosβcos(a+β)-sin(a+β)sin(-β)=cosβcos(a+β)+sin(a+β)sinβ=cosβ(cosacosβ-sinasinβ)+(sinacosβ+cosasinβ)sinβ=cosa（cosβ）^2-sinasinβcosβ+sinasinβ...