basic geometrical ideas

BASIC GEOMETRICAL IDEAS

GENERAL DETAILSPupil teacher’s name : Pooja bindal Shalu verma

GENERAL DETAILSSubject : MathematicsClass : 6th Topic : Basic geometrical ideas Duration : 35 minutes

GENERAL OBJECTIVES Pupil will be able to :- Understand the properties of

quadrilaterals.Distinguish between different types

of quadrilaterals.Grasp the concept of symmetry in

different types of quadrilaterals

What is geometry ?Geometry is the branch of mathematics which deals with properties and relations with the lines , angles ,surfaces and solids. Just as Maths deals with numbers , geometry deals with figures , points and lines…….

POINT A point is usually represented by a small dot.By a sharp tip of the pencil, mark a dot on the

paper. Sharper the tip, thinner will be the dot.

Line SegmentA line segment corresponds to the

shortest distance between two points. The line segment joining points A and B

is denoted by AB

This shortest join of point A to B(including A and B) shown here is a lineSegment.

AB

LineA line is obtained when a line segment like

AB is extended on both sides indefinitely; it is denoted by AB or sometimes by a single small letter like l.

AB AB

Intersecting LinesTwo distinct lines meeting at a point are called

intersecting lines.

L1

L2

P

Parallel LinesTwo lines in a plane are said to be parallel if

they do not meet.

Identify parallel lines

RayA ray is a portion of a line. It starts at one

point (called starting point) and goes endlessly in a direction.

A

P Twopoints are shown on the ray. They are (a) A, the startingpoint (b) P, a point on the path of the ray.We denote it by AP.

some models for a ray

Beam of light froma light house

Ray of lightfrom a torch

Sun rays

POLYGON A polygon is a simple closed curve made up of line

segments.(i) The line segments are the sides of the polygon.(ii) Any two sides with a common end point are adjacent sides.(iii) The meeting point of a pair of sides is called a vertex.(iv) The end points of the same side are adjacent vertices.(v) The join of any two non-adjacent vertices is a diagonal.

Angles

An angle is made up of two rays starting from a common end point.

Two rays OA and OB make AOB(or also ∠called BOA).∠

o

A

B

∠AOB ANGLE AOB

The meeting point of a pair of sides is called a vertex.

The end points of the same side are adjacent vertices

TrianglesA triangle is a three-sided polygon

The three sides of the triangle AB , BC and CA . The three angles are ∠BAC, BCA and ABC∠ ∠ . The points A, B and C are the vertices of the triangle

QuadrilateralsA four sided polygon is a quadrilateralIt has 4 sides and 4 angles.

Four sides AB, BC , CD and DA.

Four angles A , B, C ∠ ∠ ∠and D∠

AB and DC are opposite sides

∠A and C, ∠ ∠D and B are opposite angles∠

CirclesA circle is a simple closed curve which is not a polygon.Parts of circle 1.Centre - The fixed point 2.Radius- fixed distance 3.Diameter -A diameter is a chord passing through the center 4.Chord-line segment joining any two points on the circle. 5.Circumference – distance around the circle.

The fixed point is the center The fixed distance is the radius A diameter is a chord passing through the center of the circle. A chord of a circle is a line segment joining any two points on the circle.The distance around the circle is the circumference.

1.Centre - o2.Radius - r3.Diameter - d4.Chord - ca5.cirumference

or

d

c

a

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 iscalled a sector.

A region in the interior of a circle enclosed by a chord and an arc is called a segment of the circle.

Learning outcomeStudents will be able to Understand the concept of point ,

line , line segment , ray ,angle , triangle , quadrilateral and circle.

Apply the knowledge in different situations.

Thankyou