Hello,

I'm really stuck on this problem which I need for a project, I do feel like I'm missing something obvious...

Say I have an arc on a plane in 3D Cartesian space, with a radius of $\displaystyle r_{1}$ and an angle of $\displaystyle \alpha_{1}$ (in radians). Say I extruded a surface out of that arc perpendicular to the arcs plane, and then drew another arc on the surface with a radius of $\displaystyle r_{2}$ and angle of $\displaystyle \alpha_{2}$. Both arcs would share an endpoint in the Cartesian space. What is the formula for the length of the second arc in the Cartesian space?

Forgive me if my terminology is a little off, I'm using CAD terminology.

Thanks very much in advance for your help.