Category Archives: enlargement

Visualising Enlargements

I had always used Geogebra for this in the past, but now I’ve found this site, I don’t think I’ll bother with that any more.  This has all the settings and options you need. You could get students up to the board to draw on where they think the enlargement will be prior to revealing it.  Or show the enlargement but not the ray lines and they have to work out where the centre of enlargement is.  There are also lots of nice examples to do on worksheets on the site. (click the home button)Screen Shot 2015-11-02 at 21.15.33

One of the many good resources on the NGfL Cymru site.  Shame they don’t exist as an organisation any more but luckily their resources live on!

Extending Transformations

All four transformations (Translation, Reflection, Rotation, Enlargement) with Year 10. It feels like one of those topics that we cover in Year 8, they mostly grasp some of the skills but then forget the details (e.g. to specify the centre of rotation). That’s OK, I reckon. But it does imply that the time in Year 8 is better spent mastering the more tricky skills like reflecting in 45 degree lines than answering GCSE style questions, e.g doing translations using vectors.  These sheets are an old favourite which are great for practising those skills.

I was a bit surprised how long my middle set took to get to grips with it. Inevitably there were some who finished quickly because they found it easier to visualise than others. I was a bit stumped for how to extend it. A quick conversation in the maths office gave me the idea of multiple translations. Of course! Do, say, a reflection followed by a rotation. And then what is the single transformation that has the same effect?

I created a simple extension question:

The shape ABCD has coordinates (-1,1) (-3,1)
(-3,4) and (-1,5) respectively. It is reflected in the line y = x to produce shape A’B’C’D’ and then rotated 900 anticlockwise about (2,2) to create A’’B’’C’’D’’.

What are the coordinates of each of the points A’’, B’’, C’’, D’’ after these TWO transformations?

Describe fully the single transformation which would map ABCD onto A’’B’’C’’D’’.

This document can easily be printed and chopped. I used this geogebra file to create it.Screen Shot 2015-03-25 at 18.47.35

It’s easy to create more questions like this by moving the points of the original shape and changing the transformations in the Geogebra file.