Fill in the missing blanks below to prove that the Sum of the measures of the interior angles of a triangle is 180°. (PLEASE HELP ME FILL IN THE MISSING BLANKS AND EXPLAIN)
Let ABC be any triangle. Draw line DE, which passes through point A, parallel to line AB or AC with a compass and straightedge. According to the Angle Addition Postulate ∡DAC + ∡CAB + ∡BAE = ∡DAE. ∡DAC is congruent to ∡BCA by Alternate Interior Angles. ∡BAE is congruent to ____________ by the same theorem. Substitution allows me to replace ∡DAC with ∡BCA and ∡BAE with ∡ABC in the equation. Therefore, ____________________

Question

Fill in the missing blanks below to prove that the Sum of the measures of the interior angles of a triangle is 180°. (PLEASE HELP ME FILL IN THE MISSING BLANKS AND EXPLAIN) 
Let ABC be any triangle. Draw line DE, which passes through point A, parallel to line AB or AC with a compass and straightedge. According to the Angle Addition Postulate ∡DAC + ∡CAB + ∡BAE = ∡DAE. ∡DAC is congruent to ∡BCA by Alternate Interior Angles. ∡BAE is congruent to ____________ by the same theorem. Substitution allows me to replace ∡DAC with ∡BCA and ∡BAE with ∡ABC in the equation. Therefore, ____________________

anonymous · Answer

@ganeshie8 may you please help/check my answers?

anonymous · Answer

@ybarrap @amistre64 @Owlcoffee May you guys help me please?

dn_20 · Answer

I think this question have a problem because when line DE intersect A, DE // AB or AC by compass or straightedge. It is impossible because the line ED intersected A, so there's no way that DE// AB or AC.