2. Fill in the missing blanks below to prove that the Sum of the measures of the interior angles of a triangle is 180°.
Let ABC be any triangle. Draw line DE, which passes through point A, parallel to _______ with a compass and straightedge. According to the Angle Addition Postulate ∡DAC + ∡CAB + ∡BAE = ∡DAE. ∡DAC is congruent to ∡BCA by . ∡BAE is congruent to ____________ by the same theorem. Substitution allows me to replace ∡DAC with ∡BCA and ∡BAE with ∡ABC in the equation. Therefore, __________________________= ∡DAE. By definition of a straight angle, ∡DAE measures _____

Question

2. Fill in the missing blanks below to prove that the Sum of the measures of the interior angles of a triangle is 180°. 
Let ABC be any triangle. Draw line DE, which passes through point A, parallel to     _______ with a compass and straightedge. According to the Angle Addition Postulate ∡DAC + ∡CAB + ∡BAE = ∡DAE. ∡DAC is congruent to ∡BCA by             . ∡BAE is congruent to ____________ by the same theorem. Substitution allows me to replace ∡DAC with ∡BCA and ∡BAE with ∡ABC in the equation. Therefore, __________________________= ∡DAE. By definition of a straight angle, ∡DAE measures _____