求曲线的极坐标方程,虽然在方法和步骤上和求直角坐标方程有类似之处,然而由于极坐标系中点的坐标的多值性使曲线的极坐标方程与直角坐标系中的方程有不同的性质,情况比较复杂,因而求曲线的极坐标方程是教学中的难点,另外由于利用极坐标系来研究某些曲线比用直角坐标系方便,例如等速螺线有一个简单的极坐标 Although the polar equations of the curve are similar in terms of methods and steps to the rectangular coordinate equation, the polar coordinates of the coordinates in the polar coordinate system and the equations in the rectangular coordinate system Due to the different nature, the situation is more complicated. Therefore, the polar equation of the curve is a difficult point in teaching. In addition, it is more convenient to study certain curves using polar coordinates than to use a rectangular coordinate system. For example, a constant velocity spiral has a simple polar coordinate.