# Introduction to Triangles

In this section we will discuss about introduction to triangles.A plane figure formed three non-parallel line segments is called a triangle.

Go to top of page Go to middle of page Go to bottom of page 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.

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

• 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