Unit 1, Lesson 13
Adding the Angles in a Triangle
Accelerated 7
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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.
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.
Enter the three angle measures for your triangle on the table your teacher has posted.
A
If we experiment with angles in a triangle, we find that the sum of the measures of the three angles in each triangle is
Through experimentation we find:
If we add the three angles of a triangle physically by cutting them off and lining up the vertices and sides, then the three angles form a straight angle.
If we have a line and two rays that form three angles added to make a straight angle, then there is a triangle with these three angles.