已知3/2π
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已知3/2π已知3/2π已知3/2πsin(π/2-β)cos(a+β)-sin(a+β)sin(2π-β)=cosβcos(a+β)-sin(a+β)sin(-β)=cosβcos(a+β)+sin
已知3/2π
已知3/2π
已知3/2π
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+sinasinβcosβ+cosa(sinβ)^2
=cosa =1/3
3/2π