Parallelograms - 2
Calculate a Parallelogram - 2 sides & angle

1. Generate side lengths and angle between.

• Click on the New Dimensions button (and wait 2 secs).  

   

REMEMBER: You can always click on undo (top right) to undo your last action.

2. Construct a parallelogram as in the previous activity with the dimensions just generated.

3. Mark your dimensions.

• Right-click on the base line, click on Properties,

Select "Show Label" and then click on the down next to Name and select Value. Hit Enter. You should now see the base length.

• Right-click on one of the sides, click on Properties,

Select "Show Label" and then click on the down next to Name and select Value. Hit Enter. You should now see the side length.

• Right-click on the angle, click on Properties,

Click on the down next to Name and select Value. Click and drag the size over to 60. Hit Enter. You should now see the angle.

4. Calculate the perimeter of your parallelogram and then click on Show Perimeter to check your work.

   

Notice that we do not know the height of the parallelogram so we cannot yet calculate its area!

5. Draw the height of the parallelogram.

We draw a base line through A and B and then a line passing through our last vertex F and perpendicular to AB. We find the intersection point F of these two lines and then draw a segment from F to G.

• Click on Line2pt "Line through 2 points" icon and then click on A and B.

Click on perpendicula "Perpendicular line" icon and then click on E and then on the line AB.

Click on Intersect "Intersect two objects" icon and then click on the perpendicular line and on the line AB. The point G will be drawn!

• Click onsegment"Segment through 2 points" icon and then click on E and F.

6. Clean up

7. Find the height using GeoGebra -otherwise we need trigonometry!

• Right-click on the height, that is on the segment EF and click on Properties, Select "Show Label" and then click on the down next to Name and select Value. You should now see the height!

   

9. Play with your parallelogram.

• Click and drag any blue point (A moves the parallelogram , B rotates the parallelogram). Notice that the height never changes since it is completely defined by the length of the two adjacent sides and the angle between them.

• Click on Reset to start over.

                    
Sorry, the GeoGebra Applet could not be started. Please make sure that Java 1.4.2 (or later) is installed and activated. (click here to install Java now)

      LFS , Created with GeoGebra