The two column proof has shown that ∠DFG and ∠DEF are supplementary
How to prove the angles?
The two column proof to show that ∠DFG and ∠DEF are supplementary are as follows:
Statement 1: ∠DFE ≅ ∠DEF → m∠DFE ≅ m∠DEF
Reason 1: Base angles of an Isosceles triangle are congruent
Statement 2: ∠DFG and ∠DFE are supplementary → m∠DFG + m∠DFE = 180°
Reason 2: Definition of supplementary angles
Statement 3: m∠DFG + m∠DEF = 180°
Reason 3: Substitution
Statement 4: ∠DFG + ∠DEF = 180°
Reason 4: ∠DFG and ∠DEF are supplementary