2cos(-π+β)+5sin(π/2+β)=2(cosπ*cosβ+sinπ*sinβ)+5(sin(π/2)*cosβ+cos(π/2)*sinβ)=-2cosβ+5cosβ=3cosβ=3*(-⅓)=-1.
2cos(-π+β)+5sin(π/2+β)=2(cosπ*cosβ+sinπ*sinβ)+5(sin(π/2)*cosβ+cos(π/2)*sinβ)=-2cosβ+5cosβ=3cosβ=3*(-⅓)=-1.