What are inradius?

Some articles on inradius:

Tangential Quadrilateral - Inradius
... The inradius in a tangential quadrilateral with consecutive sides a, b, c, d is given by where K is the area of the quadrilateral and s is its semiperimeter ... quadrilateral with given sides, the inradius is maximum when the quadrilateral is also cyclic (and hence a bicentric quadrilateral) ... of the tangent lengths, the incircle has radius The inradius can also be expressed in terms of the distances from the incenter I to the vertices of the tangential quadrilateral ABCD ...
Malfatti Circles - Radius Formula
... a, b, and c of the triangle, the inradius r, the semiperimeter, and the three distances d, e, and f from the incenter of the triangle to the vertices opposite sides a, b, and c respectively ... triangle with side lengths 28392, 21000, and 25872 has inradius 6930 and Malfatti radii 3969, 4900, and 4356 ... As another example, the triangle with side lengths 152460, 165000, and 190740 has inradius 47520 and Malfatti radii 27225, 30976, and 32400 ...
Further Formulas For General Euclidean Triangles
... The following formulas involve the circumradius R and the inradius r where ha etc ... from the circumcenter to the three sides equals the sum of the circumradius and the inradius ... where R is the circumradius and r is the inradius ...