In this tutorial we will construct a triangle and measure its internal angles.
- Click on File Menu and select New. (This will open a new GeoGebra window)
- Click on the drop down arrow of the Line through Two Points and choose the Segment between Two Points button
- Construct a triangle using Segment between Two Points button. You will see in the Algebra Window , the three segments (sides of triangle) are represented by their lengths.
- To see which length corresponds to which side , click on the Move Tool (arrow) and hover the mouse over one of the sides to see the corresponding length light up.
- Now to measure internal angles of the triangle , select the Angle Button and click once on vertices B , A and C in that order. This will give you measure of ∠BAC. (Make sure that you select the vertices in clockwise direction. Anti-clockwise selection will give you reflex angle.
- Similarly, measure ∠CBA and ∠ACB.
- Now, drag the vertices using Move Button (Arrow). If you drag enough, you will notice reflex angles appearing. To stop this, right click on an angle in Algebra or Geometry Window, and choose Object Properties.Under Basic Tab un-check the Allow Reflex Angle check box and close the Object Properties box.
- Check your settings have been applied by dragging the vertices of your triangle.