Students will to explore the Triangle Sum Theorem. They will use sliders to analyze different features of an Isosceles Triangle. Then, they will apply the Triangle Sum Theorem to multiple angles of B to prove the theorem always holds true.

1. Look at the angles of the Triangle. Classify the triangle as Acute, Equilateral, or Isosceles.
2. Use the slider to see how the angles relate to one another. What happens when Angle B equals zero?
3. Now, use the slider to change angle B to multiple angles. The Triangle Sum Theorem states, “The sum of the interior angles of any triangle is equal to 180 degrees.” Based on your findings, does the Triangle Sum Theorem hold true?
4. Use the GeoGebra to create an acute angle. Measure the angles to ensure all the angles are less than 90 degrees. Add the sum of the angles. Does the Triangle Sum Theorem hold true?
5. Now create an equilateral triangle. Measure the angles to ensure all the angles are equal. Add the sum of the angles. Does the Triangle Sum Theorem hold true?