Many times, students memorize three different formulas for inside angles: (1) The central angle and the arc it opens up to have the same measure, (2) An inscribed angle is half the measure of the arc it opens up to, (3) When two chords intersect inside a circle, the angle is half of the sum of the subtended arcs.
This visual allows one to explore inside angles of all kinds, and a corresponding visual helps verify that in fact all three formulae boil down to "The angle is the average of the arcs"!
