Class 9th Math Triangles NCERT Notes CBSE 2023
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Triangles Class 9 Notes

Triangles Class 9 Notes

Chapter 7 Triangles 

The word "triangle" is a closed figure made up of three sides and corners. Students have already been introduced to drawing in previous chapters. Math for Grade 9 Chapter 7 provides a more detailed understanding of the properties of triangles.

NCERT notes for Class 9 Chapter 7 cover all text exercises presented in this article. Students are encouraged to carefully practice NCERT Grade 10 Mathematics Chapter 7 notes to gain a conceptual understanding of the topic. Experienced subject matter experts have prepared notes at Vidyakul to help students prepare for exams. Students can also visit Vidyakul to improve their preparation by practicing over 1920 questions from 47 different books for free. Read on to get NCERT Math notes Chapter 7.


Points to Remember

To help guide students in their exam preparations for NCERT 9th Maths Chapter 7 Triangles, we have provided some of the important points to remember below:

  • A plane figure bounded by three lines in a plane is called a triangle.

  • A triangle, no two of whose sides are equal, is called a scalene triangle.

  • A triangle whose two sides are equal is called an isosceles triangle.

  • A triangle whose all sides are equal is called an equilateral triangle.

  • A triangle with one right angle is called a right triangle.

  • The sum of the three angles of a triangle is 180°.

  • If a side of a triangle is produced, the exterior angle so formed is equal to the sum of the two interior opposite angles.

  • Two figures are congruent if they are of the same shape and of the same size.

  • Angles opposite to equal sides of a triangle are equal.

  • Sides opposite to equal angles of a triangle are equal.

Students can visit Vidyakul to get free access to all the important points for NCERT Class 9 Maths Chapter 7.

Topics and Sub-topics

Connect the three points to get a triangle. There are many types of triangles, such as an isosceles triangle with two sides equal in length and an equilateral triangle with all sides equal in length. In this chapter, we study congruent triangles. Triangles congruent means that the sides and interior angles of the two triangles are the same. In this chapter, students are asked to prove that any two triangles are congruent. Students learn various theorems that can be used to prove that triangles are congruent.

Students can visit Vidyakul for free access to interactive 3D videos that illustrate all 9th-grade math chapters and topics in a fun way.

Students can also check the table below to find out the important topics covered in NCERT Class 9 Maths Chapter 7:

Exercise No

Topic Name


Congruence of Triangles


Criteria of Congruence of Triangles


Properties of a Triangle


RHS and SSS Criteria for Congruence


Inequalities in a Triangle


Learn more about these congruency rules in Triangles Class 9 Notes pdf.

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Triangles Class 9 Maths Notes Part -1

Triangles Class 9 Maths Notes Part -2

Triangles Class 9 Maths Notes Part -3