# Introduction to Triangles

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In this section we will discuss about introduction to triangles.

A plane figure formed three non-parallel line segments is called a triangle.

Non-collinear points join to form a Triangle. Parts of Triangles :

Vertices : A, B, C

Sides : AB, BC , CA

Angles : ∠BAC, ∠ABC, ∠ACB.

Opposite Sides : side opposite to
∠BAC ----> BC
∠ABC ----> AC
∠ACB ----> AB

Interior and Exterior Of Triangle

In triangle ABC, there are three parts :

Interior region : The points lie inside the region enclosed by triangle.
On the sides : The points lie on the sides of the triangle.
Exterior region : The points lie outside the region enclosed by triangle.

Example Interior points : P and S

Exterior points : Q

On the sides : R and T

Triangular region

The interior of Δ ABC together with the ΔABC itself, is called the triangular region ABC.

Practice

In the given triangle ABC answer the following questions: (i) Side opposite to angle Q.

(ii) Vertex opposite to Side QR.

(iii) Angle opposite to side PR.

(iv) All six elements of triangle PQR.

(v) Name the points which are in the interior region of ΔPQR.

(vi) Name the points which are in the exterior region of ΔPQR.

(vii) Name the points which are on the ΔPQR.

(i) Side opposite to angle Q.

(ii) Vertex opposite to Side QR.

(iii) Angle opposite to side PR.

(iv) All six elements of triangle PQR.

(v) Name the points which are in the interior region of ΔPQR.

(vi) Name the points which are in the exterior region of ΔPQR.

(vii) Name the points which are on the ΔPQR.

Triangles

Introduction to Triangles
Types of Triangles on the basis of Sides
Types of Triangles on the basis of Angles
Angle Sum Property of Triangles
Exterior and Interior angles of Triangle
Triangle Inequality Property
Congruent Triangles
Postulates of Congruent Triangle
Inequality in Triangle

Geometry