Use this trick so you don't get mixed up doing matrix transpositions - 21 GIFs That Explain Mathematical Concepts

Hypotrochoid - A roulette traced by a point attached to a circle of radius (r) rolling around inside the fixed circle of radius (R) where the point is a distance (d) from the center of the interior circle

Glass wall panel installation by UK based artist Chris Wood. She uses dichroic glass, developed in the late fifties by NASA to protect against the potentially harmful effects of direct sunlight and cosmic radiation.