[Math] what does “arc” in arcsin, arccos, arctan stands for

Question

I was just wondering, what does the "arc" in arcsin, arccos, arctan stands for? Is there any particular reason why it is named the way it is?

Answer 1

Each of the "original" functions you're inverting takes an angle, so the inverse returns an angle. But thanks to the arc length formula $s=r\theta$, that's equivalent to specifying an arc length.