Comparison between Thingys

We talked in class about how the pythagorean theorem and equation of a circle were the same thing, right? The equation of a circle I think, is essentially of the same form as the distance formula. And the distance formula is the same as the pythagorean theorem, correct? They're all related, if not the same thing, extremely similar. All of the above share the same concept, if I'm right. But really, what do I know?

Circle Thing

Here is a picture of a real life example of a circle: a clock. Why didn't the first one publish??