A fraction is 0 when the numerator, here , is 0.
It does not exist (is undefined) when the denominator, here , is 0.
Find the points on the curve where the tangent is horizontal or vertical. If you have a graphing device, graph the curve to check your work. (Enter your answers as a comma-separated list of ordered pairs.)
I'm assuming setting the parametric derivative to 0 would get the horizontal tangent. But how about finding the vertical tangent (undefined)?