Angles and Triangles

Presented By, Krishna kumari

and Z,verghese KendriyaVidyalaya,

I N S Hamla.

WE CAN DRAW A LINE SEGMENT ON A PAPER AND IT HAS DEFINITE LENGTHA RAY AND LINE HAVE NO DEFINITE LENGTH

TWO RAYS AND LINE SEGMENTS WITH THE COMMON END POINT

FORM AN ANGLE

A WHERE TWO END POINTS MEET IS

CALLED VERTEX

AND LINE SEGMENTS ARE CALLED ARMS

ACUTE ANGLE

A

B C

RIGHT ANGLE

A

B C

OBTUSE ANGLE

A

B C

Triangles-Introduction

• Definition: A plane figure bound by three lines in a plane is called a triangle.a triangle has 6 parts.(3sides & 3angles).

• Here,AB,AC&BC are the sides,A,B & C are points. A

B C

Triangle Definition: A triangle, HAS THREE LINE SEGM ENTS ,THR EE VERTIC E S

AN D THR EE ANGLES

A

B C

Types Of TrianglesOn the basis of sides: 1. Scalene triangles 2. Isosceles triangles 3. Equilateral triangles.On the basis of angles: 4.Acute triangles 5.Right triangles 6.Obtuse triangles.An equilateral triangle is an isosceles triangle but the converse

is not true.

Scalene Triangles• Definition: A triangle,no two of whose sides are equal, is called a scalene

triangle. E.g..

A

B

C

Isosceles Triangle Definition: A triangle, two of whose sides are equal, is called an isosceles

triangle.e.g.

A

B C

Equilateral Triangle• Definition: a triangle whose all sides are equal, is called an

equilateral triangle.e.g.

A

B C

Acute triangle• Definition:A triangle each of whose angles is acute is called an acute angled

triangle or simply acute triangle.e.g.

A

B C

Right Triangle• Definition: A triangle with one angle a right angle is called a right angled

triangle or simply right triangle.e.g.

A

B C

Obtuse triangle• Definition: A triangle with one angle an obtuse angle is known as obtuse

angled triangle or simply obtuse triangle.e.g.

A

B C

Triangle properties-1• Property 1:the sum of the three angles in a triangle is 180 degrees.

• Property 2:if a side of a triangle is produced then the exterior angle so formed is equal to the sum of the two interior opposite angles.

A

B C

Here, angle A+angle B+angle C=180 degrees.

A

B CD

Here,angle ACD = angle A+angle B