Difference between revisions of "Circle"

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m (changed brd* to b as names for instances of board in the example codes)
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Then we construct a circle through "A" and "B". The setting of a new color and changing the stroke-width is not necessary.
 
Then we construct a circle through "A" and "B". The setting of a new color and changing the stroke-width is not necessary.
 
<source lang="javascript">
 
<source lang="javascript">
var ci = brd.createElement('circle',["A","B"], {strokeColor:'#00ff00',strokeWidth:2});
+
var ci = b.createElement('circle',["A","B"], {strokeColor:'#00ff00',strokeWidth:2});
 
</source>
 
</source>
  
Line 29: Line 29:
  
 
<source lang="javascript">
 
<source lang="javascript">
var ci2 = brd2.createElement('circle',[p1,p2],  
+
var ci2 = b.createElement('circle',[p1,p2],  
 
     {strokeWidth:3, dash:2, fillColor:'#ffff00', fillOpacity:0.3});
 
     {strokeWidth:3, dash:2, fillColor:'#ffff00', fillOpacity:0.3});
 
</source>
 
</source>
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<source lang="javascript">
 
<source lang="javascript">
var ci3 = brd3.createElement('circle',[p1,p2],  
+
var ci3 = b.createElement('circle',[p1,p2],  
 
     {strokeWidth:1, fillColor:'#555500', fillOpacity:function(){ return p2.X()*0.25;} });
 
     {strokeWidth:1, fillColor:'#555500', fillOpacity:function(){ return p2.X()*0.25;} });
 
</source>
 
</source>

Revision as of 20:46, 20 October 2008

Circle through two points

One possibility to construct a circle is to give its center and a point defining its radius. Lets construct two points "A" and "B".

var b = JXG.JSXGraph.initBoard('jxgbox', {originX: 200, originY: 100, unitX: 50, unitY: 50});
var p1 = board.createElement('point',[0,0], {name:'A',style:6});
var p2 = board.createElement('point',[2,-1], {name:'B',style:6});

Then we construct a circle through "A" and "B". The setting of a new color and changing the stroke-width is not necessary.

var ci = b.createElement('circle',["A","B"], {strokeColor:'#00ff00',strokeWidth:2});

Generally it is better to use JavaScript variables and not Geometry-Element names when constructing. Now, we do the same examples with JavaScript variables. To show other variations, we use a dashed stroke style and set a fill color.

var ci2 = b.createElement('circle',[p1,p2], 
    {strokeWidth:3, dash:2, fillColor:'#ffff00', fillOpacity:0.3});

Dynamic fill-opacity

We can make the fill-opacity dynamic and make it dependent on the position of "B", i.e. the JavaScript variable "p2".

var ci3 = b.createElement('circle',[p1,p2], 
    {strokeWidth:1, fillColor:'#555500', fillOpacity:function(){ return p2.X()*0.25;} });