Is there a way to prove that angle B and angle C are equivalent in this situation? The argument my textbook made certainly seemed to imply that, and it really bothers me that I can't quite see it. I'm worried it's really simple and I'm overthinking it... I haven't taken geometry in nearly ten years but I tried to review the basics.
To be clear, the arc is all part of one circle (if that matters) and there are no parallel or perpendicular lines (aside from the perpendicular radius to tangent).
Any help is greatly appreciated!