First, students will learn what the perpendicular bisector theorem is, and why it's true. Then students will learn what the converse of the perpendicular bisector theorem is, and why it's true. Before attempting to understand these proofs, students must know the definition of perpendicular bisector, the isosceles triangle theorem, and the SAS congruence theorem.

Watch the first part of this video:

Circumcenter of a triangle by Khan Academy

Conclude by giving your students these challenges:

- Complete the Square by NRICH
- Eleven by NRICH
- About Average by NRICH
- 2015 AMC 8, Problem 4
- Pay My Name by Pierce School: Problem / Solution