﻿ Similarity and Enlargement | Mathematics Form 2

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#### Similarity and Enlargement - Mathematics Form 2

Lesson objectives

By the end of the lesson, you should be able to:

(i) Identify similar figures

(ii) Apply enlargement in a cartesian plane.

SIMILARITY AND ENLARGEMENT

In real life situations we encounter objects which have the same shape.The objects are said to be similar

Determining centre of enlargement and scale factor

Find the centre and scale factor of enlargement for triangle xyz with vertices X(2,3), Y (2,5) and Z(3,3) and its image x1y1z1 with vertices X1 (3,4), Y1 (3,8) and Z1 (5,4).

Solution

Join x to x1 and y to y1 and produce them to meet at point O. The centre of enlargement. The coordinates of O are O (1,2).
O is (1,2)

To find the scale factor of enlargement
Measure lines OX, OX1, OY, OY1, OZ and OZ1.
Note that
OX1OY1  = OZ1 =  2
OX   OY    OZ
The scale factor of an enlargement is +2.  This is a positive enlargement.

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