# Draw a radius

Many theorems can be proven, and puzzles solved, by making a single creative step, from which everything else falls out. The purpose of this article is to show examples of where the creative step is simply drawing a radius. Whenever you see a circle, you should ask "would drawing a radius help?" Here is one such puzzle:

Notice that once the radius \(\overline{OB}\) has been drawn, the solution falls out easily.