1. The problem statement, all variables and given/known data P is the part of the curve 9y²=4x³ between the points (1,-2/3) and (1,2/3). Evaluate the integral $$\int_P x ds $$ 2. Relevant equations 3. The attempt at a solution $$\int_P x ds = \int_P x |r'(t)| dt $$ My problem is that I cannot find a right parametrization r(t) for this. I tried y=t, then x=((3/2)t)^(2/3) but thent goes from -2/3 to 2/3, but that gives a complex x for t=-2/3 Tried it with x=3t² and y=2sqrt(3)t³, I get the same problem. Any tips ? Thanks!