# Chapter 4 Basic Geometrical Ideas Class 6 Notes Maths

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**Chapter 4 Basic Geometrical Ideas Class 6 Notes Maths**will let you know important concepts embedded in the chapter in a precise manner. This make easier for the students to comprehend the concepts due to use of easy language.Â Class 6 Maths Revision Notes will help the students to recall information with more precision and faster.Â Also, NCERT Solutions for Class 6 Chapter 6 Maths that will serve as beneficial tool that can be used to recall various questions any time. It will allow the students to evaluate their learning immediately.**Introduction**

â€¢ The term â€˜Geometryâ€™ is the English equivalent of the Greek word â€˜Geometronâ€™. â€˜Geoâ€™ means Earth and â€˜metronâ€™ means Measurement.

**Point**

â€¢ A point determines a location and has no length, breadth and height. Usually denoted by a single capital letter like A, B, C.

**Line Segment**

â€¢Â A part of a line is called a line segment. It is the shortest distance between two points.

**A Line**

â€¢Â A line is a straight one- dimensional figure that has no thickness and extends endlessly in both directions.

**Intersecting Lines**

â€¢ If two lines have one common point, they are called intersecting lines.

**Parallel Lines**

â€¢Â Two parallel lines in a plane do not meet each other.

â€¢ The perpendicular distance between two parallel lines is the same throughout.

**Curves**

â€¢ Any drawing (straight or non straight) done without lifting the pencil. This means, in mathematics, a line is also a curve.

â€¢ A simple curve is one that does not cross itself.

â€¢ A curve is said to be closed if its ends are joined.

â€¢ A curve is said to be open if its ends are open.

â€¢ Polygon is a simple closed curve made up of line segments. Sides: The line segment forming a polygon.

â€¢ Vertex: The meeting point of a pair of sides.

â€¢ Adjacent sides: Any two sides with a common end point.

â€¢ Adjacent vertices: The end points of the same side of a polygon.

â€¢ Diagonal: The line joining any two non-adjacent vertices.

**Angles**

â€¢ An angle is made up of two rays starting from a common initial point.

â€¢ The two rays forming the angle are called the arms or sides of the angle.

â€¢ The common initial point is the vertex of the angle.

â€¢ A triangle is a three-sided polygon.

â€¢ A four sided polygon is a quadrilateral. It has 4 sides and 4 angles.

**Circles**

â€¢Â A circle is a simple closed curve which is not a polygon.

â€¢ The path of a point moving at the same distance from a fixed point. The fixed point is the centre.

â€¢ Radius: A line segment that connects the centre to a point on the circle.

â€¢ Diameter: A line segment passing through the centre and having its end points on the circle.

â€¢ Chord: A line segment connecting any two points on a circle.

â€¢ A diameter is a chord passing through the centre of a circle. It is a longest chord of a circle.

â€¢ Arc: A portion of a circle.

â€¢ Sector: A region in the interior of a circle enclosed by an arc on one side and a pair of radii on the other two sides.

â€¢ Segment: A region in the interior of a circle enclosed by an arc and chord.

â€¢ Circumference: The distance around a circle.

â€¢ Semi-circle: A diameter of a circle divides it into two equal parts, each part is a semi-circle.