Draw the locus of a fixed point on a rolling disc.
Challenging Problem #2 Intro
If a goat was tied around a tree, and the rope remains taut, the goat's locus would be a circle (See Animation below). You could think of the goat like the Earth orbiting the Sun.
Challenging Problem #2 (Application: Retrograde of Jupiter)
Let's imagine that the planets (Goats) orbiting around the Sun (Tree). What would the locus of the orbit of Jupiter look like in a Geocentric Model (i.e. The Earth is stationary)?