AoPSWiki

NEW! NEW! NEW!
Want to learn how to tackle those tough AMC/AIME/Olympiad algebra problems? Check out Art of Problem Solving's NEW Intermediate Algebra by Richard Rusczyk and Mathew Crawford. Over 1600 problems!

Personal tools

Log in

Search

Toolbox

Inradius

From AoPSWiki

The inradius of a polygon is the radius of its incircle (assuming an incircle exists). It is commonly denoted $r$ .

Properties

If $\triangle ABC$ has inradius $r$ and circumradius $R$ , then $\cos{A}+\cos{B}+\cos{C}=\frac{r+R}{R}$ .

Retrieved from "http://www.artofproblemsolving.com/Wiki/index.php/Inradius"

Category: Geometry

NEW! NEW! NEW!
Want to learn how to tackle those tough AMC/AIME/Olympiad algebra problems? Check out Art of Problem Solving's NEW Intermediate Algebra by Richard Rusczyk and Mathew Crawford. Over 1600 problems!

© Copyright 2008 AoPS Incorporated. All Rights Reserved. • Foundation • Privacy • Contact Us