√3=tan60原式=sin40(sin10/cos10-sin60/cos60)=sin40(sin10cos60-cos10sin60)/cos10cos60=sin40sin(10-60)/cos10cos60=-sin40sin50/(1/2*cos10)=-sin40cos40/(1/2*cos10)=-1/2*sin80/(1/2*cos10)=-1/2*cos10/(1/2*c...