关于直线参数方程x=x_0+tcosα y=y_0+tsinα,一般都把点(x_0,y_0)作为定点,但在研究某些二次曲线按给定条件的弦的中点轨迹时,若能辩证地把定点(x_0,y_0)、作为变化着的中点,仍然利用直线的这种参数方程,也能顺利地找到x_0和y_0的关系式,从而得到点(x_0,y_0)的轨迹方程。 Regarding the linear parametric equation x=x_0+tcosα y=y_0+tsinα, the point (x_0, y_0) is generally used as a fixed point, but in the study of the midpoint trajectory of a certain quadratic curve given the conditions of the string, if we can dialect The fixed point (x_0, y_0) is used as the changing midpoint, and the parametric equation of the straight line is still used, and the relation between x_0 and y_0 can be found smoothly, and the trajectory equation of the point (x_0, y_0) can be obtained.