Let's say I take a flat circle (a planar dimension) and cut off the top of the circle in a straight line from point A of the arc to point B of the arc.

The distance from one edge of the circle (A) to the other (B) is 506 feet, that being measured in a straight line from the start of the arc to the end of the arc. Call it the "base" of the arc.

Now, let's assign the height from midline of the straight line to midline of the arc, and set that figure to 27 feet. This is a perpendicular height from the base to the highest point of the arc segment.

How would I calculate the distance from A to B along the curved segment? What is the formula?

I got out my Pocket Ref, but couldn't figure it out.

Steve