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Triangles

ICSE · Class 9 · Mathematics

Quick revision notes for Triangles — ICSE Class 9 Mathematics. Key concepts, formulas, and definitions for last-minute revision.

45 questions25 flashcards5 concepts

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A labeled diagram showing the vertices, sides, and angles of a basic triangle ABC.
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Key Topics to Revise

1

Introduction and Basic Properties

  • A triangle is a plane figure bounded by three straight line segments
  • Every triangle has three vertices, three sides, and three angles
  • The sum of all angles in any triangle is always 180°
2

Relationship Between Sides and Angles

  • In a triangle with unequal sides, the greater side has the greater angle opposite to it
  • In a triangle with unequal angles, the greater angle has the greater side opposite to it
  • If two sides are equal, their opposite angles are also equal (isosceles triangle property)
3

Median and Altitude

  • A median joins a vertex to the midpoint of the opposite side
  • Every triangle has three medians that intersect at the centroid
  • The centroid divides each median in the ratio 2:1
4

Congruent Triangles

  • Two triangles are congruent if they have the same shape and size
  • Congruent triangles can be superimposed exactly on each other
  • Corresponding parts of congruent triangles are equal (CPCTC)

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Full Notes

Key Concepts

A triangle has three verticesIn a triangleA median connects a vertexAn altitude is the perpendicular fromTwo triangles are congruent if they

Frequently Asked Questions

What are the important topics in Triangles for ICSE Class 9 Mathematics?
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 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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