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.