| A | B |
|---|
| perpendicular bisector | segment, ray, line, or plane perpendicular to a segment at its midpoint |
| equidistant from two points | a point if its distance from each point is the same |
| distance from a point to a line | the length of the perpendicular segment from the point to the line |
| equidistant from two lines | when a point is the same distance from one line as it is from another line |
| perpendicular bisector of a triangle | a line (or ray or segment) that is perpendicular to a side of the triangle at the midpoint of the side |
| concurrent lines | when three or more lines (or rays or segments) intersect in the same point |
| point of concurrency | point of intersection of concurrent lines |
| circumcenter of a triangle | point of concurrency of the perpendicular bisectors of a triangle |
| angle bisector of a triangle | bisector of an angle of a triangle |
| incenter of the triangle | point of concurrency of angle bisectors |
| median of a triangle | segment whose endpoints are a vertex of the triangle and the midpoint of the opposite side |
| centroid of a triangle | point of concurrency of the medians of a triangle |
| altitude of a triangle | perpendicular segment from a vertex to the opposite side or to the line that contains the opposite side |
| orthocenter of a triangle | point of concurrency of the altitudes of a triangle |
| midsegment of a triangle | segment that connects the midpoints of two sides of a triangle |
| indirect proof | proof in which you prove that a statement is true by first assuming that its opposite is true |
