Page 155 - New Medley 5 Semester 2

Regions of a Triangle P

The shaded portion shown in the figure is called the
A
interior of ∆PQR. Points C and D lie in the interior B H
region of ∆PQR. G

The points P, B, Q, F, R and H lie on the boundary of C D
this triangle. Q F R
E

The region beyond the boundary of a triangle is called the exterior of the
triangle. Here, points A, E and G lie in the exterior of ∆PQR.

Types of Triangles

A triangle has six elements – three sides and three angles. Triangles are

classified on the basis of measures of their sides and angles.

Classification of Triangles on the Basis of Sides

On the basis of sides, triangles are classified into three kinds.

1. Equilateral triangle: A triangle having equal length of A

sides is called equilateral triangle. This is a regular
triangle. That means, it has three sides and three

angles of equal measure.

In equilateral triangle ABC,
B C
AB = BC = AC
P
Also, A = B = C (= 60°)

2. Isosceles triangle: A triangle that has any two sides of equal
length is called isosceles triangle.

In isosceles triangle PQR, PQ = PR
Q R
If we measure Q and R, we find that Q = R

X

3. Scalene triangle: A triangle in which all the three
sides are of unequal length is called scalene triangle.
Y Z

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