Radius of incircle and circumradius of a triangle

Radius of incircle and circumcircle of an equilateral triangle

The sum of inradius and circumradius of incircle and circumcircle of a regualr polygon of side n is

Ratio of inradius to circumradius in triangle

in a triangle ABC , let angle C = (pi)/(2) if r the in radius and R is the circumradius of the triangle ABC , then 2( r+R) equals

Find the radius of incircle it the sides of triangle are (i) (13,14,15)