SUBJECT: MATHEMATICS
CLASS:� JSS 1
DATE:
TERM: 3rd TERM
REFERENCE TEXTBOOKS�
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WEEK THREE
TOPIC: Geometry Plane Shapes
Plane shapes are two-dimensional shapes bounded by lines known as sides. Any shape drawn on a plane is called a two-dimensional shape (or 2-D shapes for short). When we say a figure is two- dimensional, we mean it can be measured along x and y axes i.e. it has length and width or breadth.
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Types of Plane Shapes
Common plane shapes are:
Triangles and quadrilaterals are examples of polygon. However, because triangles and quadrilaterals have their own special properties they are usually dealt with separately.
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Triangles
Tri-angle means three angles. A triangle has three angles and three sides.
Types of Triangles
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Other types of triangles are:
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Quadrilaterals
A quadrilateral is a four-sided plane shape with four angles
Types of quadrilateral�
Properties
Properties�
It is a quadrilateral that has opposite sides equal and each angle is 900.
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It has two opposite sides parallel and equal in length
Properties
A trapezium is a quadrilateral with one pair of opposite sides parallel
Note: when the two non-parallel sides are equal in length, it is called an isosceles trapezium
A kite is a quadrilateral that has two pairs of adjacent sides equal in length and one pair of opposite angles equal.
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Evaluation:
Polygon
A polygon is any closed shape that has three or more straight sides. Thus, rectangles, squares and triangles are all examples of polygons.
The table below shows some special polygons and their sides.
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Names of Polygons | � | Number of sides |
Triangle | � | 3 |
Quadrilateral | � | 4 |
Pentagon | � | 5 |
Hexagon | � | 6 |
Heptagon | � | 7 |
Octagon | � | 8 |
Nonagon | � | 9 |
Decagon | � | 10 |
Duo decagon | � | 12 |
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There are two types of polygons. They are:
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When the sides of a polygon and the included angles are not equal it is called an irregular polygon. Examples are irregular pentagon and irregular hexagon shown below.
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Irregular� Pentagon
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A polygon that has all its sides and angles equal is called a regular polygon. Examples of regular polygons are: equilateral triangle, square, regular pentagon, hexagon, etc
Regular Hexagon � � � � � � � � � � � � � � � � � � � � � � � � � regular pentagon
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Circles
A circle is a plane shape that has set of points equidistant from a fixed point, O. The fixed point is the centre of the circle as shown in the diagram below.
Diameter
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The parts of a circle
The circumference is the distance around the circle.
A radius (plural radii) is any straight line joining the centre of the circle to any point on the circumference.
A chordis any straight line joining two points on the circumference.
A diameteris any chord that goes through the centre of the circle.
Regions
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A sectoris the region between two radii and the circumference.
A semicircleis a sector between a diameter and the circumference, i.e. half a circle.
A segment is the region between a chord and the circumference.
Evaluation:
Draw a circle and include the following parts: two radii, a sector, a chord, a segment, a diameter and an arc. Label each part and shade any regions.
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General Evaluation/ Revision Questions
Reading Assignment
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Weekend Assignment�
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Theory
Write down the missing word in the following
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