IM 8.1.15 Lesson: Adding the Angles in a Triangle

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GeoGebra Classroom Activities

Complete the table by drawing a triangle in each cell that has the properties listed for its column and row. If you think you cannot draw a triangle with those properties, write “impossible” in the cell.

Share your drawings with a partner. Discuss your thinking. If you disagree, work to reach an agreement.

Your teacher will give you a card with a picture of a triangle. The measurement of one of the angles is labeled. Mentally estimate the measures of the other two angles.

  1. The measurement of one of the angles is labeled. Mentally estimate the measures of the other two angles.
  2. Find two other students with triangles congruent to yours but with a different angle labeled. Confirm that the triangles are congruent, that each card has a different angle labeled, and that the angle measures make sense.
  3. Enter the three angle measures for your triangle on the table your teacher has posted.
You can use the applet below to store your information.

You are given three angles in the applet below. Can you make a triangle from each set that has these same three angles?

Here is a quadrilateral. Its tears are marked with different colors and those are lined up below.

What do you notice?

Move the angles to get different quadrilaterals. Do you have a conjecture about the angles?

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