The slide

To draw a circle, given the centre and a point on the circle

In this case you can use a  ‘slide’.

A ‘slide’ is a  square of suitable material, with a small hole approximately in the centre, which can be wedged into the cut out section  of the polyMath. The sides of the square should be just over 1.1cm.

Suitable materials

The material needs to be  about 2 mm thick and capable of being compressed slightly. You should be able to slide it along the section.

Cardboard  and PVC from a plastic mat (if the plastic is transparent , all the better)  work well.

 

Using The “Slide”

To draw a circle where       o        is the centre and          x           is a point on the circle.

 

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1.   Position the polyMath as below.

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2.   Note the approximate position of     x      in relation to the ruler. ( Here this is at about the 3.8 cm mark)

3.   Lift the polyMath and wedge the slide in position with the hole opposite the mark you noted. (here 3.8 cm).

4.   Replace the polyMath and move the slide and/or the polyMath slightly until you can see the point.

     x       through the hole in the slide.

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5. Using two pencils as normal, draw the circle.

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