Definitions [5]
Define a triangle.
A plane figure bounded by three lines in a plane is called a triangle. The figure below represents a ΔABC, with AB, AC andBC as the three line segments.
A triangle (denoted by the symbol △) is the simplest closed shape in geometry. It is a two-dimensional figure made by connecting three points that do not lie on the same straight line (non-collinear).
An exterior angle is formed when a side of a triangle is extended beyond its vertex. The angle created between the extended side and the adjacent side of the triangle is the exterior angle.
An altitude of a triangle is a straight line from one vertex, drawn perpendicular (at 90°) to the opposite side (or to its extension)
- Orthocentre: The altitudes of a triangle pass through exactly one point; that means they are concurrent. The point of concurrence is called the orthocentre.
The line segment joining a vertex of a triangle to the midpoint of its opposite side is called a median of the triangle.
- The point where all three medians meet is called the centroid.
