We already know how to compute one simple arc length, that of a line segment. If the endpoints are $$P_0(x_0,y_0)$$ and $$P_1(x_1,y_1)$$ then the length of the segment is the distance between the points, $$\sqrt{(x_1-x_0)^2+(y_1-y_0)^2}$$, from the Pythagorean theorem, as illustrated in Figure $$\PageIndex{1}$$.