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Isosceles Triangles

ICSE · Class 9 · Mathematics

Complete topic list for Isosceles Triangles in ICSE Class 9 Mathematics. Key concepts, sub-topics, and what to focus on for board exams.

45 questions22 flashcards5 concepts

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A labeled diagram illustrating an isosceles triangle with two equal sides and the angles opposite to them also being equal. Includes the definition of an equilateral triangle as a special case.
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4 Topics · ICSE Class 9 Mathematics

Topics in Isosceles Triangles

1

Basic Definitions and Introduction

  • An isosceles triangle has at least two equal sides
  • An equilateral triangle is a special case of isosceles triangle where all three sides are equal
  • In an isosceles triangle, the equal sides are called arms and the third side is called the base
2

Theorem 1: Equal Sides → Equal Angles

  • If two sides of a triangle are equal, then angles opposite to them are also equal
  • This is the fundamental property of isosceles triangles
  • Proof uses construction of perpendicular from vertex to base
3

Theorem 2: Equal Angles → Equal Sides

  • If two angles of a triangle are equal, then sides opposite to them are also equal
  • This is the converse of Theorem 1
  • Proof uses construction of perpendicular from vertex to base
4

Properties and Important Results

  • The angle bisector from vertex of isosceles triangle bisects the base at right angles
  • The perpendicular bisector of base passes through the vertex
  • The line joining midpoint of base to vertex is perpendicular to base and bisects vertex angle

Key Concepts

A triangle with at least twoA triangle with all three sidesIf two sides of a triangleIf two angles of a triangleThe angle bisector from the vertex

Frequently Asked Questions

What are the important topics in Isosceles Triangles for ICSE Class 9 Mathematics?
Isosceles Triangles covers several key topics that are frequently asked in ICSE Class 9 board exams. Focus on the core concepts listed on this page and practise related questions to build confidence.
How to score full marks in Isosceles Triangles — ICSE Class 9 Mathematics?
Start by understanding all key concepts. Practise previous year questions from this chapter. Revise formulas and definitions regularly. Use flashcards for quick revision before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

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