我们知道,平面直角坐标系中,经过定点p_0(x,y),倾角是θ(0≤θ≤π)的直线(如图)的参数方程是其中t是参数,它的几何意义是:|t|的大小等于定点p_0(x_0,y_0)到动点p(x,y)的距离,而t表示有向线段p_0p的数量,p点在P_0点的上方t为正,p点在p_0点的下方t为负。 We know that in the plane rectangular coordinate system, the parametric equation of the straight line passing through the fixed point p_0(x,y) and the inclination angle θ(0≤θ≤π) (as shown in the figure) is where t is a parameter and its geometric meaning is: The size of t| is equal to the distance from fixed point p_0(x_0,y_0) to the point p(x,y), and t represents the number of directed segments p_0p. p is the positive point above point P_0, and p is at p_0. The bottom t is negative.