1. Recap: This circle has a diameter of 1. What is its circumference? 1

2. Recap. This circle has a radius of r. What is its circumference? r

3. Approximating the Area of a Circle. Imagine splitting a circle with radius r into 1 million triangles. r

4. What can you tell me about the area of each triangle? r

5. Each triangle is approximately ½ × base × radius r

6. The base of the triangle is approximately : Circumference 1 million Why?

7. So the total area is: 1 million × ½ × × r

8. So the total area is: π r 2

9. What is the area of this circle? 4