Remember that polar coordinates are about replacing x and y as coordinates for a point on a plane by instead r, r and theta,which is the angle measured counterclockwise from the positive x-axis.
极坐标是关于r,θ的,用r,θ代替平面上一点的x,y坐标,是从原点到那一点的距离,,which,is,the,distance,from,the,origin,to,a,point,θ是由x轴逆时针旋转,而得到的夹角。