4855 /www/nrich/html/content/id/4855/ 1 2011-02-01T00:00:01 <?xml version="1.0" encoding="UTF-8"?> <mdoxml version="1.0"><p><a href="https://nrich.maths.org/8045">First Forward Into Logo</a><br></br> <strong>Previous:</strong><a href="http://nrich.maths.org/public/viewer.php?obj_id=4858&amp;part="> FF5</a></p> <p> </p> <p>In FF4 you investigated the instruction:<br></br> <br></br> REPEAT 360 [FD 1 RT 1]<br></br> <br></br> Hopefully you altered it as you saw fit and produced some exciting shapes. So it is timely to introduce you to the idea of a variable . As the word implies, a <span style="font-weight: bold;">variable</span> is something that varies, something that changes.<br></br> <br></br> You may find the following a quicker way of drawing circles and circular patterns. It is called a <span style="font-weight: bold;">procedure</span> and has to be written in a particular way.<br></br> <br></br> TO CIRCLE :CH<br></br> REPEAT 360 [ FD :CH RT 1]<br></br> END<br></br> <br></br> Notice how the procedure is set out:<br></br> First a title / a command TO CIRCLE<br></br> then the variable :CH<br></br> followed by the instructions REPEAT 360 [ FD :CH RT 1]<br></br> then a formal closing of the procedure END<br></br> <br></br> N.B. the variable, :CH could have been any letter or letters that you wish!</p> <p> </p> <br></br> <table style="" border=""> <tbody> <tr> <td> <div>Now experiment with the procedure:</div> <br></br> <div>CIRCLE 3</div> <div>CIRCLE 6</div> <div>CIRCLE -3</div> <div>CIRCLE 9</div> </td> <td><mdo:image alt="circles" height="146" src="logo6.gif" width="207"></mdo:image></td> </tr> </tbody> </table> <br></br> <p>Building on this idea of a procedure we could have written:<br></br> <br></br> TO CIRC :CH :ANG<br></br> REPEAT 360 [ FD :CH RT :ANG]<br></br> END<br></br> <br></br> This is a procedure with two variables!<br></br> <br></br> Can you anticipate what will change and what will happen now?<br></br> Can you see what is now possible?<br></br> Go on experiment! Try:<br></br> CIRC 3 3<br></br> CIRC 3 6<br></br> CIRC 3 30<br></br> <br></br> What is happening?</p> <table style="" border=""> <tbody> <tr> <td> <div>Why not be bolder and try say:</div> <div>CIRC 30 90</div> <div>CIRC 30 45</div> <div>CIRC 30 18 etc., etc.,</div> </td> <td><mdo:image alt="polygons" height="249" src="logo7.gif" width="316"></mdo:image></td> </tr> </tbody> </table> <br></br> <p>What do you notice?<br></br> What conclusions can you come to?<br></br>  </p> <p> </p> <p><strong>Next:</strong><a href="http://nrich.maths.org/public/viewer.php?obj_id=4856&amp;part="> FF7</a><br></br>  </p> <p> </p></mdoxml> 2 3 0 0 1 1 1 Learn to write procedures and build them into Logo programs. Learn to use variables. Algebra Introducing algebra Information and Communications Technology Logo Using, Applying and Reasoning about Mathematics Practical Activity