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Part 1 – Enlargement by a positive scale factor (no centre of enlargement)

Part 2 – Enlargement by positive and negative scale factors with a centre of enlargement

• Drag the cross to move the centre of enlargement around
• Drag the slider to change the scale factor
• Tick the box to show the enlargement
• Show/hide the vector from the centre of enlargement to a vertex by simply clicking on the vertex
• You can use the zoom buttons to zoom in or out, and pan across the grid by clicking and dragging
• You can reduce distractions and focus on a single point by ticking the box in the top right. This enables you to look at how enlargement affects just point A.

Pantographs

Pantagraphs are devices made up of an extending and collapsing lattice of rhombi. They can be used to create enlargements. Pantographs have been used by artists and cartographers to create copies of sketches and maps—larger, smaller, or the same size. In the below applet, the lattice is set so that we end up an enlargement of scale factor -2, with the centre of enlargement being the fixed red point. Try tracing over the flag slowly, using the blue point.

Engravers have used similar pantographs (in “reverse” so the scale factor as an absolute value less than 1) to engrave tiny lettering on plaques and trophies.