1. In a triangle, the perpendicular line from a vertex to the opposite side
geometric mean
2. for any positive real numbers a, b, and x, if then x is called the geometric mean between a and b. Notice that
Projection of a point on a line
3. the point where a perpendicular through the point to the line intersects the line
altitude of a triangle
4. the portion of a line with endpoints that are the projections of the endpoints of the segment
Projection of a segment on a line