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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

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