Answer: The conventional practice is to select the coordinate points of the plane rectangular coordinate system, the positive semi-axis of X axis and the positive semi-axis of Y axis according to the meaning of the geometric problem, establish the plane rectangular coordinate system, determine the coordinates of each point according to the meaning of the problem, or set the coordinates of a certain point, so as to find out the coordinates of the relevant points and the equation of the straight line where the line segment is located according to the meaning of the problem, and achieve the purpose of solving the problem.