Cass 7 Maths online solutions-Triangle and its properties

Cass 7 Maths online solutions-Triangle and its properties

Chapter 6 – Triangle and its properties Introduction

Exterior angle of a triangle and its properties

An exterior angle of a triangle can be formed by extending the sides of a triangle at its vertex. A triangle can have three exterior angles.

An exterior angle of a triangle is equal to the sum of its interior opposite angles.

Proof:-

Given – Consider ∆ABC

∠ACD is an exterior angle

To Show:-

M ∠ACD=m ∠A +m ∠B

Through C draw CE parallel to BA

∠1= ∠X (BA is parallel to CE and AC is a transversal so the alternate angle should be equal)

∠2= ∠y (BA is parallel to CE and AD is a transversal so the corresponding angle should be equal)

∠1+ ∠2= ∠x+ ∠y

As we know ∠x+ ∠y=m ∠ACD

So, ∠1+ ∠2= ∠ACD

Hence proved

The above relation proved between an exterior angle and its two interior opposite angles are referred as the exterior angle property of a triangle.

For examples and practice questions click on CBSE Class 7th Maths.

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