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Interactivity - Construct a parallelogram ABCD with vertices A, B and C
Directions for interactivity
In the top right: Reset button  to start over or Undo button  to undo last step.
First draw sides \overline{AB} and \overline{BC} How?
- Select the line segment tool
 and click on A and then on B (they will glow).
- You will get a line segment a joining A and B.
- Click on B and then on C.
- You will get a line segment b joining B and C.
Now pick any of the 3 ways below to draw a parallelogram. You will always get the point D(-3,4)!
One way to draw the parallelogram (based on definition that opposite sides are parallel). How?
- Select the parallel line tool
 and click on point A and then on line b.
- You will get a line c passing through A and parallel to b=\overline{BC} .
- Click on point C and then on line a.
- You will get a line d passing through C and parallel to a=\overline{AB} .
- Click on the intersection tool
 and then click on the intersection point of c and d.
- You will get the point D at (-3,4).
Another way to draw the parallelogram (based on definition that opposite sides are the same length). How?
*Select the compass tool  and click on center point A and then on B and on C.
- You will get a circle c with center A and radius the length of b=\overline{BC} .
- Click on point C and then on A and on B
- You will get a circle d with center C and radius the length of a=\overline{AB} .
- Click on the intersection tool and then click on the intersection point of c and d.
- You will get the point D at (-3,4).
A third way to draw the parallelogram (based on definition that the diagonals bisect each other). How?
- (With the line segment tool still selected, draw the diagonal c=\overline{AC} .
- Select the midpoint tool
 and click on c.
- You will get the midpoint D of b=\overline{AC} . Right-click on the label "D", select rename and type in E and click on OK.
- Click on the line tool
 and click on B and then on E to get the line d.
- Click on the circle-center-point tool
 and then click on E and then on B.
- You will get a circle e with center E and radius the length of a=\overline{EB} . (It will pass through B.)
- Click on the intersection tool and then click on the intersection point of line d and circle e.
- You will get the point D at (-3,4).
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How to save interactivity
- To save and then use the saved file, you will need to download and install GeoGebra
- If there is a menubar, click on File -> Save.
- If there is no menubar, double-click anywhere in the interactivity. A separate GeoGebra window will open (with menubar).
Click on File -> Save.
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Leigh Lara — 12 November 2008, 20:54
Up one level
