sinx+siny=2/5、cosx+cosy=2√3/5,
∴siny=2/5-sinx,①
cosy=2√3/5-cosx,②
①^2+②^2,1=18/25+1-(4/5)sinx-(4√3/5)cosx,
∴sinx+√3cosx=9/10,
∴sin(x+60°)=9/20.
sinx+siny=2/5、cosx+cosy=五分之二根号三、、、求sin(x+60)=?
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