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
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

Lines and Angles
Key topics include:

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

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
Key topics include:

• Introduction
• Parallelogram
• Rectangle
• Square
• Rhombus
• Trapezium
• Kite
• Theorems on Parallelograms
Key topics include:

• Area Axioms
• Area of Polygonal Regions
• Base & Altitude of a Parallelogram
• Base
• Altitude
• Theorems on Triangles & Quadrilaterals
Circles
Key topics include:
• Basic Definitions
• Arcs of a Circle
• Sectors of a Circle
• Segments of a Circle
• Theorems on Circles
• Chords Properties of Circles
• Theorems on Congruent Circles
• Theorems on Angle Subtended by Arcs

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As per CBSE syllabus, the only chapter under this topic is Number System. Key topics...