平面坐标系中两点A（X1,Y1）,B（X2,Y2）.从A作X轴的平行线,从B作Y轴的平行线,两直线相交于点C,则C（X2,Y1）.AC=|x1-x2|,BC=|y1-y2|.在直角三角形ABC中,由勾股定理可得：AB^2=AC^2+BC^2=(x1-x2)^2+(y1-y2)^2AB=根号[(...