JSS2 Second Term Basic Technology Lesson Note – Enlargement and Reduction of Plane Figures

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 WEEK FIVE

CLASS:  JS TWO

TOPIC: ENLARGEMENT AND REDUCTION OF PLANE FIGURES

SUB-TOPICS:

1. Enlargement/Reduction of plane figures
2. The Radial Method and Method of Length of Side

Content Development (NOTES FOR FIRST LESSON/PERIOD ONE)

Sub-Topic I: Enlargement/Reduction of plane figures

An object is enlarged when all of its dimensions are changed in the same ratio. Thus, enlargement is also called transformation. Each length of the objects is multiplied by the same number called scale factor to obtain the enlargement.

When the scale factor is less than one, the original objects is reduced. i.e., Scale Factor = length of enlargement/corresponding length.

Examples of enlargement/reduction of plane shapes include:

ENLARGEMENT

i) Drawing a triangle which is twice the size of the original triangle

Procedure;

1. Draw the given triangle ABC
2. Draw DB perpendicularly to AB, such that BD=AB
3. With center A, and radius AD, draw an arc to meet AB at E
4. From E, draw EF parallel to BC, with F on line AC
5. Draw lines to join AEF to give the triangle double in size

ii) Drawing a square which is twice the size of the original square

Procedure;

1. Draw the given square ABCD
2. Draw one of the diagonals, AC.
3. With A as center, and radius AC, draw an arc to meet AD at E.
4. AE is one side of the square.

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