# Finding Formula for Circle Area via Triangle

- Author:
- Brad Ballinger

## Circle - Triangle Transformation

## Questions to guide your thinking

Suppose the circle has radius r.
How long is the short leg of the triangle?
What part of the circle has the same length as the long leg of the triangle?
What is the area of the triangle?
What is the area of the circle?
Harder questions:
How do we know it's a triangle?
How can a change like this not affect area?
How was this thing made?