Triangle [i]ABC[/i] has been translated along the directed line segment from [i]B[/i] to [i]C[/i] to make triangle [i]A'B'C'[/i] and triangle [i]ABC [/i]was also translated along the directed line segment from [i]A[/i] to [i]C[/i] to make triangle [i]A''B''C''[/i]. [br][br]Use what you know about vertical angles to prove the Triangle Angle Sum Theorem.