For a cylinder of radius r and two points P1 and P2 on it, the geodesic on the cylinder co...

For a cylinder of radius r and two points P1 and P2 on it, the geodesic on the cylinder connecting P1 to P2 is the curve on the cylinder of least length joining P­1 to P2. Show that the length of the geodesic on the cylinder with axis the w-axis and radius r that joins two points (r, θ1, w1) and (r, θ2, w2) is