Sum of Interior Angles of a Triangle

1. What do you predict will happen to the sum of the three interior angles as the triangle changes shape?
2. Do you think a narrow triangle and a wide triangle will have the same angle sum? Explain why.

Move the vertices to create several different triangles. Were your predictions correct? Use your observations as evidence.

If you move the point to change the original triangle, what happens to angle ?

What is the sum of all the interior angles of a triangle?

Do you think it is possible to have a triangle with angles 50°, 60°, and 80°? Explain.

Respond to the questions with always, sometimes or never 1. A triangle can have an obtuse angle. 2. A triangle can have an acute angle. 3. A triangle can have two obtuse angles. 4. A triangle can have two acute angles. 5. A triangle can have three acute angles.

If you knew an angle in a triangle was 30° and the second and third angles were congruent, what would each missing angle be?

If you knew an angle in a triangle was 120° and the second angle was twice as big as the third angle, what would each be?