I determined and what next? A circle inscribed in a triangle This is a circle that touches all sides of the triangle. The center of the circle inscribed in the triangle ABC is the intersection of the axes of the angles of the triangle ABC (and always lies inside the triangle!). Radius is the distance from the center to either side of the triangle. how to calculate, you will find in "Sample solutions of the 2nd series of the summer part of KMS 2009 / 2010.pdf example no.6" in Slovak