Escherized Double Rotations
Choose from 3, 4, 5, or 6-fold rotations. One of those doesn't work in general. Been looking at a lot of quilts lately, is all I can say. (Cf.
Ellipse inscribed in irregular convex quadrilateral
Battleship: Polar Coordinate Style (V2)
Taylor Series for e^x
Chord of a Circle 1
Thin Slice Pythagorean Discovery
Polar Coordinates (Calculus 2)