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PPT: The Triangles and its properties

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 Page 1


INTRODUCTION
Polygon
Polygon is a simple close curve formed by the line segments is 
called a polygon. Triangle s a polygon with least number of 
lines
Triangle
? A plane figure formed by three non parallel line segment 
is called a triangle
Elements of triangle
? The three sides AB,BC,AC and angle abc,, angle bac and angle 
acb denoted by angle a, angle b and angle c together is known as 
six part of or elements of triangle abc
a
b c
Page 2


INTRODUCTION
Polygon
Polygon is a simple close curve formed by the line segments is 
called a polygon. Triangle s a polygon with least number of 
lines
Triangle
? A plane figure formed by three non parallel line segment 
is called a triangle
Elements of triangle
? The three sides AB,BC,AC and angle abc,, angle bac and angle 
acb denoted by angle a, angle b and angle c together is known as 
six part of or elements of triangle abc
a
b c
TYPES OF TRIANGLES
(BASED ON ITS SIDES)
Page 3


INTRODUCTION
Polygon
Polygon is a simple close curve formed by the line segments is 
called a polygon. Triangle s a polygon with least number of 
lines
Triangle
? A plane figure formed by three non parallel line segment 
is called a triangle
Elements of triangle
? The three sides AB,BC,AC and angle abc,, angle bac and angle 
acb denoted by angle a, angle b and angle c together is known as 
six part of or elements of triangle abc
a
b c
TYPES OF TRIANGLES
(BASED ON ITS SIDES)
EQUILATERAL TRIANGLE
? Equilateral triangle: A triangle with three congruent (equal) 
sides and three equal angles
These marks indicate equality.
A
B
C
Page 4


INTRODUCTION
Polygon
Polygon is a simple close curve formed by the line segments is 
called a polygon. Triangle s a polygon with least number of 
lines
Triangle
? A plane figure formed by three non parallel line segment 
is called a triangle
Elements of triangle
? The three sides AB,BC,AC and angle abc,, angle bac and angle 
acb denoted by angle a, angle b and angle c together is known as 
six part of or elements of triangle abc
a
b c
TYPES OF TRIANGLES
(BASED ON ITS SIDES)
EQUILATERAL TRIANGLE
? Equilateral triangle: A triangle with three congruent (equal) 
sides and three equal angles
These marks indicate equality.
A
B
C
ISOSCELES TRIANGLES
? At least two sides are the same length
5
A
B C
Page 5


INTRODUCTION
Polygon
Polygon is a simple close curve formed by the line segments is 
called a polygon. Triangle s a polygon with least number of 
lines
Triangle
? A plane figure formed by three non parallel line segment 
is called a triangle
Elements of triangle
? The three sides AB,BC,AC and angle abc,, angle bac and angle 
acb denoted by angle a, angle b and angle c together is known as 
six part of or elements of triangle abc
a
b c
TYPES OF TRIANGLES
(BASED ON ITS SIDES)
EQUILATERAL TRIANGLE
? Equilateral triangle: A triangle with three congruent (equal) 
sides and three equal angles
These marks indicate equality.
A
B
C
ISOSCELES TRIANGLES
? At least two sides are the same length
5
A
B C
SCALENE TRIANGLES 
? Scalene triangle: A triangle that has no congruent (equal) 
sides
A
B
C
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FAQs on PPT: The Triangles and its properties

1. What are the different types of triangles classified by their sides and angles?
Ans. Triangles are classified into six main types: by sides (equilateral, isosceles, scalene) and by angles (acute, right, obtuse). Equilateral triangles have all three equal sides, isosceles have two equal sides, and scalene have no equal sides. Acute triangles have all angles less than 90°, right triangles have one 90° angle, and obtuse triangles have one angle greater than 90°.
2. How do I find the sum of angles in a triangle for CBSE Grade 8?
Ans. The sum of all interior angles in any triangle always equals 180°. This angle sum property holds true regardless of the triangle's type or size. To verify this property, students can measure angles using a protractor, then add them together. Understanding this fundamental triangle property helps solve problems where one or two angles are unknown.
3. What's the difference between median and altitude in a triangle?
Ans. A median connects a vertex to the midpoint of the opposite side, while an altitude is a perpendicular line from a vertex to the opposite side (or its extension). Both lines originate at a vertex but serve different purposes. Medians relate to the triangle's centroid, whereas altitudes help determine height for area calculations. Every triangle has three medians and three altitudes.
4. Can a triangle have two right angles and why or why not?
Ans. No, a triangle cannot have two right angles because the angle sum property requires all three angles to equal 180°. If two angles were 90° each, their sum alone would be 180°, leaving no degrees for the third angle. This demonstrates why the triangle inequality and angle sum property restrict triangle formation, preventing impossible configurations.
5. How do the triangle inequality theorem and properties of triangles help in real geometry problems?
Ans. The triangle inequality theorem states that the sum of any two sides must exceed the third side, determining whether three lengths can form a valid triangle. This property, combined with angle properties and congruence rules (SSS, SAS, ASA, RHS), enables students to verify triangle validity, solve construction problems, and prove geometric relationships efficiently for Grade 8 mathematics.
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