First, students will learn what the alternate segments theorem is, and how to use it.
Alternate Segment Theorem by DrFrostMaths
Next, students will see two proofs of the alternate segments theorem.
Angle in the Alternate Segment Theorem by Eddie Woo
Conclude by giving your students this challenge: In the figure below, the radius of each large circle is 4. What's the radius of the small circle?

The only prereq is knowing that the centers and point of contact for touching circles are collinear. Here's the solution.
Conclude by giving your students these challenges:
- Master Minding by NRICH
- Triangles in Circles by NRICH
- 2001 AMC 8, Problem 4