Sum of a Triangle's Angles
Proving the Sum
Rotate Triangle CDE 180 degrees around the midpoint of EC.
Rotate Triangle CDE 180 degrees around the midpoint of ED.
Question 1: Proving the Sum Part 2
Explain on your paper how these rotations prove that the sum of the angles in Triangle CDE is 180 degrees.
Question 2: Finding the Missing Angles
Find the measure of the yellow angle below.
Finding Missing Angles
Question 3: Angle Relationships
Extend the sides of Triangle CDE above by using the Line tool.
Redraw this figure on your paper and fill in the measures of all missing angles.