Mathematics - Properties of Triangle Question with Solution | TestHub

There is a standard identity relating the inradius ($r$), circumradius ($R$), and the cosines of the angles of a triangle:$r=R(\cos A+\cos B+\cos C-1)$. Rearranging this formula to solve for $R(\cos A+\cos B+\cos C)$:$r=R(\cos A+\cos B+\cos C)-R$$R(\cos A+\cos B+\cos C)=r+R$.