(iii) Orthocentre of the triangle may lie inside the triangle, outside the triangle and on the triangle. (ii) All the three altitudes meet at a point H (called orthocentre of triangle) i.e., all altitudes of any triangle are concurrent. (iii) The side PQ, itself is an altitude to base QR of right angled PQR in figure. (ii) AD is an altitude, with D the foot of perpendicular lying on BC in figure. (i) PS is an altitude on side QR in figure. Altitude of a triangleĪn altitude of a triangle is the line segment drawn from a vertex of a triangle, perpendicular to the line containing the opposite side. Linear boundary of the triangle is the triangle itself.

The points lying inside ΔABC (i.e., cross) forms the interior of ΔABC and the points lying outside ΔABC (i.e., dots) forms the exterior of the ΔABC. Interior and exterior of a triangleĪ triangle drawn on a plane divides the plane into 3 parts interior, exterior, and the triangle itself. The side AB is called the base line of ΔABC and the angle formed at vertex C opposite the base line AB is called the vertical angle. (d) Sum of the angles of a triangle is 180°, i.e., ∠A + ∠B + ∠C = 180°.

(c) Number of angles are 3, i.e., ∠A, ∠B, and ∠C. (b) Number of vertices (i.e., initial and terminal points of sides) are 3, i.e., A, B, and C. (a) Number of sides forming ΔABC are 3, i.e., AB, BC, and CA. It is a 3-sided polygon and is named as ‘ΔABC’. What is the Median and Altitude of a TriangleĪ closed figure bounded by three line segments is called a triangle.