# Angle Sum Theorem

Move points

*A*,*B*, and*C*to choose the triangle size and shape you want. Move sliders and to the extreme right.- What do you observe about angles
*1*,*2*and*3*? - What is the sum of angles
*1*,*2*, and*3*? Justify your answer. - Based on your observations above, what can you say about the sum of the interior angles of a triangle? Explain your answer.