Use the derivatives of the equations that parameterize the arc.

Dear George,

I refer you to the following link which contains an example:

http://www.vbforums.com/showthread.php?609289-How-To-calculate-the-startangle-and-endangle-in-arc

Hoping this will be helpful,

Rafik

Hello George, could you provide us with a schema?

I can't figure out if differential calculus is necessary, or if trigonometry is sufficient.

Gabriel

It depends on how your arc is defined (approximately by sequence of coordinates, explicitly by parametrization, implicitly by equations), and in what space (R2, R3, ...)

I agree with you Sjoerd, we have not enogh information to give a satisfactory answer. What is an arc in this context?