polygons form 1

7/29/2019 Polygons form 1

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MATHEMATICS - FORM 1

POLYGONS


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POLYGONSA) Recognising PolygonsA polygon is a plane figure with three or

more straight edges as its sides.

For example :-

(a) (b)

(a) and (b) are polygons.


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(c) (d)

(c) and (d) are not polygons.

B) Names of Polygons1. A polygon is named after the number of

sides it contains. The following names

are given to some common polygons.

2. In general, a polygon with n sides is called

a n-gone.

For example :-

A polygon with 12 sides is called a 12-gon.

Worked Example 1

Name the following polygons.

(a)


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(b)

C) Determining the Number of Sides, Verticesand Diagonals in a given Polygon

1. A vertex is the point where two straight

lines meet.

2. A diagonal is a straight line joining two

vertices which are not adjacent to each

other.

For example :-

The quadrilateral KLMN contains

(i) 4 sides (i.e. KL, LM, MN and KN )

(ii) 40vertices (i.e. K, L, M and N )

(iii) 2 diagonals ( i.e. KM and LN )

Worked Example 2

State the number of


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(i) sides, (ii) vertices, (iii) diagonals

in each of the following polygons.

(a) (b)

3. The table below shows the number of

sides, vertices and diagonals for some

common polygons.

D) Sketching Polygons

To sketch a polygon,determine the number

of sides or vertices the polygon has first.

Worked Example 3


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Sketch two different shapes to represent the

following polygons.

(a) Quadrilateral

(b) Hexagon

Solution

(a)

(b)

SYMMETRYA) Determining and Drawing the Line(s)of Symmetry of Shapes1. An object is said to have a line of symmetry if it

can be divided into identical halves when it is

folded along that line.

For example :-

(a)


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(b)

2. An object may have more than one line of

symmetry.

For example :-

(a)

Worked example 4

Determine whether each of the following

object has a line of symmetry.

(a) (b)

Solution

Worked Example 5

Draw and state the number of line (s) of

symmetry in each of the following object.

(a) (b)


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Solution

(a) (b)

1 line of 2 lines ofsymmetry symmetry

Worked Example 6

The figurs below are drawn on square grids.

Draw and state the number of lines of symmetry

in each figure.

(a) (b)

Solution

(a)

2 lines of symmetry

(b)

4 lines of symmmetry

Worked Example 7


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The figure below are drawn on tessellation

of equilateral triangles. Draw and state the

number of lines of symmetry in each figure.

(a) (b)

Solution

(a)

2 lines of symmetry

(b)

1 line of symmetry

B) Completing a given Shape

(a)


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(b)

Solution

(a)

(b)

(a) (b)

Solution

(a) (b)


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C) Drawing Designs using theConcept of Symmetry

(a) (b)

Solution

Below are two possinble designs.

(a)

(b)


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(a) (b)

Solution

(a) (b)

10.3 TRIANGLES

A) Recognising Different Types of Trianglesand their Geometric Properties

(ii)


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(iii)

(b) The types of angles

(a) (b)


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(a) (c)

(b)

B) Determining and Drawing Linesof Symmetry of given Triangles


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(a) (c)

(b)

Solution

C) Drawing Triangles


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Solution

Step 1

Skretch the triangle.

Step 2

Draw EF = 2 cm.

Step 3

Using a protractor, draw an angle of 50 at F.

Step 4

Using a ruler, mark the point G 1 from F.


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Step 5

Join EG

Solution

Step 1

Sketch the triangle.

Step 2

Draw JK = 3 CM.

Step 3

Using a protractor, draw an angle of 30 at J.

Step 4

Using a ruler, mark the point L 1.5 cm from K.


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Step 5

Join KL.


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D) Determining the Sum of Angles of a Triangle


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E) Determining the Angles of an Equilateral Triangle

(a) (b)


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F) Determining Wheter the two Base Angles of anIsosceles Triangle are Equal


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G) Determining the Exterior and InteriorOpposite Angles of a Triangle


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H) Problem Solving involving Triangle


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10.4 QUADRILATERALS

A) Recognising Different Types of Quarilateralsand their Geometric Properties


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B) Determining and Drawing Lines ofSymmetry of given Quadrilaterals

C) Drawing Quadrilaterals


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D) Determining the Sum of Anglesof a Quadrilateral


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E) Determining whether the OppositeAngles of a Parallelogram are Equal


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F) Problem Solving involving Quadrilateral


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polygons form 1

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