Vectors For Enlargement

I'm going to produce a serial of brusque posts on approaches or methods that teachers powerfulness non lead maintain seen before. I'm really aware that at that spot volition hold upward many people who already purpose these approaches, simply I figure that non everyone volition lead maintain seen them thus they are worth sharing.

Today, vectors for enlargements. I start saw this on Twitter years agone simply I can't scream back who tweeted it (apologies!). Later I saw my old colleague Lizzie Stokes (@misstokesmaths) using this approach inward her teaching.

How I used to learn enlargement
I'll illustrate my previous method amongst a negative enlargement question:

I'd say my students to depict a business to whatever vertex from the centre of enlargement. Then I'd say them to count how many squares they've moved to larn to the start vertex. I e'er modelled this slow on the board. I showed the procedure of counting carefully ('count the corners, non the spaces!') because I uncovering they oft miscount.

Then I circled the scale component subdivision in addition to said that because the scale component subdivision is negative two, to uncovering the icon they lead maintain to double the distance from the centre of enlargement. But because it's negative, they lead maintain to larn inward the opposite direction from the centre. So inward this case, nosotros started past times going 2 units right and i unit of measurement upward thus straight off nosotros lead maintain to go four units left and 2 units down. I emphasised that we're going the opposite direction because it's a negative enlargement. We thus produce the same matter for each of the other vertices inward turn. At the end, all the corresponding vertices should hold upward joined amongst direct lines going through the centre of enlargement. If not, you've miscounted!

I'd demo around other illustration amongst a dissimilar scale factor, thus larn them to exercise a lot of these on printed worksheets. It was commonly a relatively tranquillity lesson every bit they all had to produce a lot of counting! I'd larn circular berating them for using pen when I'd told them to purpose pencil 10 K times.

In hindsight I realise that this method could hold upward better. It plant fine for super smart students (most things do!), simply others struggled amongst it. One employment is that you lot lead maintain to concur lots of details inward your caput piece you lot move though the question. Another employment is that the method is dissimilar to the method for positive enlargement - there's an extra matter to remember.

How I straight off learn enlargement
They start past times labelling each vertex amongst a missive of the alphabet in addition to thus finding the vector that takes them from the centre of enlargement to each vertex. They are already fluent inward using vectors from our come about translation thus this should hold upward straightforward.

They write downwards the vectors rather than trying to concur the information inward their caput similar they did before. Then all they lead maintain to produce is multiply each of their vectors past times the scale factor, in addition to this gives them the vector for each of the vertices of the image. So they know just where to depict the icon - it's all calculated in addition to recorded earlier they start drawing.

I've used 'Year 11' vector musical note inward the film inward a higher house for clarity, though it's non essential at this stage.

This method is identical regardless of whether nosotros are enlarging amongst a positive or negative integer or a fraction. So all of a abrupt negative enlargements are no harder than positive enlargements (assuming students know how to multiply negatives). H5N1 clear in addition to consistent method all circular - I don't know why I didn't e'er produce it similar this.

Any others?
I promise that was helpful if you'd non seen it before!

I've blogged a break of times earlier almost choice methods for diverse topics (see my posts tagged 'methods'). If at that spot are whatever approaches or methods that you lot purpose that you lot mean value other teachers powerfulness non use, I'd dearest to listen them! Please comment below or electronic mail me or tweet me.