Page 60 - Maths Class 06

A
In Fig 4.17, AD is median drawn from the vertex A to side BC. Thus, BD = CD.
As a triangle has three vertices, so we can draw three medians for a triangle.
From Fig. 4.18, we see that the three medians, that is AD BE, and CF pass the through
the same point O. This point of concurrence of the medians is called the centroid. The
centroid divides the medians in the ratio of 2 : 1. A B D C
Fig. 4.17
Thus, AO = 2 OD
F O E
BO = 2 OE

CO = 2 OF
B D C
Fig. 4.18

Altitude of a Triangle

A line segment drawn perpendicular from the vertex to the opposite side is called the A
altitude of the triangle.
In the Fig. 4.19, AD is the altitude drawn from the vertex A to the opposite side BC. So
AD ^ BC. The symbol ‘^’ denotes perpendicular.
A
As a triangle has three vertices, so three altitudes can be drawn to a B D C
triangle, AD ^ BC, BE ^ AC, CF ^ AB. F E Fig. 4.19

From Fig. 4.20, we see that three altitudes meet a point O. This point of O
concurrence of the altitudes is called the orthocentre of the triangle.

B D C
Fig. 4.20

Exercise 4.2

1. Name the angles given in the following figure:
(a) (b) (c) (d) E F
Z
A R

Y
O X D
B P Q

2. Draw angles RST and MNP. Label each of them.

3. Name all possible angles in the given figure.
A

B

O
C

D

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