Geometry Grade 9 CBSE

This is one of the most important sections for Grade 9 maths. There are a number of topics covered in this section:

  1. Introduction to Euclid’s Geometry
  2. Lines and Angles
  3. Triangles
  4. Quadrilateral
  5. Area of Triangles and Quadrilaterals
  6. Circles

Click on each topic to know more details.

Introduction to Euclid’s Geometry
Key topics include:
• Basic Geometric Concepts
• Some Terms Related to Geometry
• Line Segments
• Length Axioms of Line Segments
• Ray, Half-Life & Line Separation
• Incidence Properties of Points & Lines
• Parallel Lines & Intersecting Lines
• Euclid’s Five Postulates

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Lines and Angles
Key topics include:

• Point
• Line Segments
• Angles & Their Properties
• Types of Angles
• The Angle Bisector
• Angle Relations
• Parallel Line

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Triangles
Key topics include:

  • Triangles
  1. Definition
  • Types of Triangles on the Basis of Sides
  1. Equilateral Triangle
  2. Isosceles Triangle
  3. Scalene Triangle
  4. Perimeter of a Triangle
  • Types of Triangle on the Basis of Angles
  1. Right Angled Triangle
  2. Acute Angled Triangle
  3. Obtuse Angled Triangle
  • Concurrent Lines & Various Centres of a Triangle
  1. Medians & Centroid
  2. Altitudes & Orthocentre
  3. Perpendicular Bisector of Sides & Circum-centre
  4. Angle Bisectors & In-Centre
  • Theorems on Triangles
  1. Angle Sum Theorem (Theorem 1)
  2. External Angle Theorem (Theorem 2)
  3. Corollary of Theorem 2

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Quadrilateral
Key topics include:

  • Introduction
  • Types of Quadrilateral
    • Parallelogram
    • Rectangle
    • Square
    • Rhombus
    • Trapezium
    • Kite
  • Theorems on Quadrilaterals
  • Theorems on Parallelograms

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Area of Triangles and Quadrilaterals
Key topics include:

  • Area Axioms
  • Area of Polygonal Regions
  • Base & Altitude of a Parallelogram
    • Base
    • Altitude
  • Theorems on Triangles & Quadrilaterals

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Circles
Key topics include:
• Basic Definitions
• Arcs of a Circle
• Sectors of a Circle
• Segments of a Circle
• Quadrants of a Circle
• Theorems on Circles
• Chords Properties of Circles
• Theorems on Congruent Circles
• Theorems on Angle Subtended by Arcs
• Theorems on Cyclic Quadrilateral
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