THE DIMATU

• Centralizer of an element : the centralizer of an element x in a group G is defined as the set C of elements c of G such that c and x commute.
• Centralizer of a subgroup : the centralizer of a subgroup H of a group G is defined as the set C of elements c of G such that c  commutes with every element of H.
• Centroid of a triangle : the centroid of a triangle is the intersection's point of the medians. The other name for centroid is center of mass or center of gravity.
• Circumcenter : the circumcenter of a triangle ABC is the center of the circumcircle of the triangle ABC.
• Circumcircle : the circumcircle of a triangle ABC is the circle passing by the three points A, B and C.
• Circumradius : the circumradius of a triangle ABC is the radius of the circumcircle of the triangle ABC.
• Contact triangle : the contact triangle of a triangle ABC is the triangle formed by the points of intersection of the ABC's incircle with ABC.