How does one know when the a polar curve repeats itself? I usually go from 0 to 2pi but that sometimes get me into trouble. For example: Question says find the horizontal and vertical tangents of this curve.. [tex] r=3cos\theta [/tex] I was like well.. you have horizontal tangents when [tex] \theta = \pi/2, 3\pi/2, 5\pi/2, 7\pi/2 [/tex] vertical tangets when [tex] \theta = 0, \pi/2, \pi, 3\pi/2 [/tex] until I looked at the solution manual and they have only first half of these points.. then I realized that the curve repeats itself at pi, not 2pi. So yeah any tricks to see when it ends? Thanks!