The distance formula in rectangular (Cartesian) coordinates is the Pythagorean Theorem in disguise. A lot of my students like this explanation. It helps build off of knowledge that they already have from geometry.
27 questions all stuffed in to the same circle gives students a real challenge. This puzzle is great for any high school geometry lesson on circles. It contains angles with their vertex in the circle, on the circle, and outside of the circle. These angles are all made using diameters, chords, secants and tangents.