A triangle is of course well defined by its vertices. As a set, they may be rotated, translated or reflected - the triangle will remain the same. In general, a triangle is defined by its three elements. SAS, ASA, SSS provide three well known examples. But there is much more.
R is known as circumradius , the circle as the circumcircle .
Here is the table. From time to time, I'll be adding constructions to the listed combinations. Every one is welcome to send me solutions or solved new combinations. Alexander Bogomolny 2436362 .