May 15, 2015

Area and Circumference of CirclesYou can use regular polygons with an increasing number of sides to help explain why a circle of radius 1 unit has an area of pi un^2 . Where does the “ r^2 ” come from in the formula for the area of a circle?Lessons, videos, exercises, and text from CK-12. Additional resources available at this site.

- Mathematics > General
- Mathematics > Geometry

- Grade 9
- Grade 10

Reason abstractly and quantitatively.

Construct viable arguments and critique the reasoning of others.

Model with mathematics.

Use appropriate tools strategically.

Attend to precision.

Give an informal argument for the formulas for the circumference of a circle, area of a circle, volume of a cylinder, pyramid, and cone.