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Locus

Another exclusive Foundation RISCWorld application

Exercise 5. Polar graphs

So far we have only examined standard cartesian or rectangular graph shapes. We will now consider Polar graphs.

Instead of defining the coordinates of a point in the x-y plane in terms of its horizontal and vertical coordinates, it is also possible to define the same point in terms of its distance from the origin and the angle that this line makes with the horizontal axis. Most mathematics students find this difficult at first as they have become used to the cartesian model. In fact we tend to base real life directions more on the polar than the cartesian model. For example, bearings .

1. Click on the icon on the top row containing a picture of 'r=sin2t'. This is the fourth icon from the left.
2. Turn on auto-scaling.

Note that all of the x and y range fields are now 'greyed' out but the t fields are now selectable. If you are in degrees mode, enter '0' in the tmin icon and 360 in the tmax icon, otherwise set the range to 0 to 2p. Locus uses 'p' as a constant which represents the value of pi.)

1. Set the t range
2. Click on the formula menu icon
3. Click on 't' which should be the first entry.
4. Click on <Plot>
   
   

The graph will be drawn correctly for the given range.

You should now experiment with changing the various settings to get different effects and try drawing other similar graphs both from the menu and of your own devising.

Foundation RISCWorld