Triangle Exploration

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You will be using Geometer's Sketch Pad to create a triangle. We will be measuring the angles of the triangle by using the computer's internal "protractor".


1) Go to the apple and drag down to GSP.

2) Click on the page to get rid of the logo.

3) Create three points on your screen. Label these points with your "hand" tool by clicking on each point. Go back to the "arrow" tool.

4) Click on the page to get rid of all highlighted points. Select two points (remember to hold down the shift key) and go to CONSTRUCT - LINE SEGMENT. Your computer should have drawn a line segment using the two highlighted points as endpoints. Repeat the procedure so you have a triangle on your screen.

5) Your triangle has three vertices, name the labeled vertices below:

_______, ________, and ________.


6) We are going to use the computer's measuring function to calculate the measure of our angles. We are going to select three points - the order will determine what angle you are measuring. For example if you have triangle ABC, you might measure angle ABC, angle CAB, and angle ACB. Find the measure of all three angles and record those measurements below.

1st angle _____________degrees

2nd angle _____________degrees

3rd angle _____________degrees


7) Add up the measure of the first, second and third angle and see what you get. Record your answer below.

angle 1 + angle 2 + angle 3 = ___________degrees








8) Click on your page so nothing is highlighted. Now, with your arrow tool, select a point on your triangle, move your point so you have a new triangle. Record the measure of the angles below.

1st angle _____________degrees

2nd angle _____________degrees

3rd angle _____________degrees


9) Add up the measure of the first, second and third angle and see what you get. Record your answer below.

angle 1 + angle 2 +angle 3 = ___________degrees


10) Repeat step 8 again to create a new triangle. Record your angles and sum below.

1st angle _____________degrees

2nd angle _____________degrees

3rd angle _____________degrees


angle 1 + angle 2 + angle 3 = ___________degrees

11) Repeat step 8 again to create a new triangle. Record your angles and sum below.

1st angle _____________degrees

2nd angle _____________degrees

3rd angle _____________degrees


angle 1 + angle 2 + angle 3 = ___________degrees



11) Can you make a conjecture to describe what is happening. Describe it below. Can you create a set of angles that a triangle would contain. Can you draw the triangle on your screen?