Triangle Interior and Exterior Angles Discovery
Learning Geogebra
Making Mistakes:
You are bound to make some mistakes while working. Don’t panic! Chose “Ctrl Z” or the undo arrow in the upper left corner to erase your mistake.
Menu items:
They are Clear all, Open, Save, Share, Export Image, Download As, Print
Preview.
First Drawing: Using the tools.
1) Choose Point Tool: Click on it; click in sketch area to create points.
2) Choose Segment Tool: Click on it; click the mouse in sketch area, drag and release. Construct 2 more segments.
3) Choose Circle with Center: Click on it; click mouse in sketch area. Drag and release. Construct 4 more circles.
4) Now practice erasing them by using “Crtl Z” or “undo” or “Delete”. One by one the circles should disappear.
5) Now draw three circles of different sizes that fit on the screen. Click the Move tool – this will allow you to select objects and move them around the window. Arrange the circles from smallest to largest to that they look like a snowman. To change the size of your circle, click the point on the circle and drag.
6) Use the Point Tool to put eyes, nose, mouth and buttons on your snowman.
7) Click Menu, then Download as, then select “PNG image”. Upload image into Google Classroom assignment.
In the Geometry app below,
Second Drawing: Create, Label and Transform a Triangle
1) Choose Segment Tool and construct a triangle. Be careful to start your 2nd segment exactly over the endpoint of the first segment.
2) Choose Move Tool: Click on it. Move the mouse to one of the labelled vertices of the triangle. A hand will appear. You can move the label by holding down the mouse and drag where you want the label to be. It won’t go too far from the point.
3) Choose Move Tool; click on it. Click on any point, hold down and drag to move your point.
Move the vertex of the triangle to approximate an:
a) equilateral triangle
b) obtuse triangle
c) acute isosceles triangle
4) Keep your 
to begin your 3rd drawing.
Third Drawing: Measure of Interior Angles of a Triangle
This drawing begins with . If you did not keep from the second drawing, then construct
Measure each angle of your triangle by choosing the Angle Tool under Measure.
1) Select angle ABC by click the 3 points that define the angle
(point A, then the vertex point B, then the vertex point C)
2) Repeat these steps for the other two angles.
Calculate:
1) Find the sum of all three angle measures. ( Watch the video below to see how to calculate the sum.
2) Transform the triangle’s shape by selecting any vertex and dragging it. Does the sum change?
to begin your 3rd drawing.
Third Drawing: Measure of Interior Angles of a Triangle
This drawing begins with . If you did not keep from the second drawing, then construct
Measure each angle of your triangle by choosing the Angle Tool under Measure.
1) Select angle ABC by click the 3 points that define the angle
(point A, then the vertex point B, then the vertex point C)
2) Repeat these steps for the other two angles.
Calculate:
1) Find the sum of all three angle measures. ( Watch the video below to see how to calculate the sum.
2) Transform the triangle’s shape by selecting any vertex and dragging it. Does the sum change?
Quick (Silent) Demo
Question 1
Select the MOVE 
tool. Move any one (or more) of the triangle's vertices around.
What can we conclude about the interior angles of this triangle? Be specific in your response.
In the Geometry app below:
Question 2
Select the MOVE tool. Move any one (or more) of the triangle's vertices around. Transform the triangle by selecting any vertex and dragging it. What is the relationship you notice between the 2 interior angles and the exterior angle? Be specific in your response.
