How to sum the x or the y coordinate of an arbitrary number of points.
Let's say that I have a list of i+1 points: P_0, P_1, P_2, ... P_i-1, P_i. I want to sum the x (or the y) coordinate of all these points using the operation "Sum". I would be tempted to type something like:"Sum(x(P_n),n,0,i)", but it doesn't work. How can I sum all these coordinates (without typing:"x(P_0)+x(P_1)+x(P_2)+...+x(P_i-1)x(P_i)")?
Thanks in advance.