Hi, what do you want to do?
PBS
Telling Time on a Torus
What shape do you most associate with a standard analog clock? Your reflex answer might be a circle, but a more natural answer is actually a torus. Surprised? Then stick around.
msvgo
Equivalence Relations and Classes
It explains the conditions for a relation to be equivalence relation through solved examples. It also explains equivalence classes and provides examples based on it.