正准线是圆锥曲线的重要元素之一。在解题中,若能适当地应用准线的几何意义,常可寻求较简单的解法,从中得到解题方法上的启迪。以抛物线的准线为例加以说明。 Positive alignment is one of the important elements of the conic curve. In the problem-solving, if we can properly apply the geometric meanings of the quasi-line, we can find a simple solution, from which we can get enlightenment of the solution method. Take the parabolic guideline as an example.