Question

Given: ∠ABC ≅ ∠DEF and ∠GHI ≅ ∠DEF

Prove: m∠ABC = m∠GHI

We are given that angle ABC and
are congruent, and that angle GHI and angle DEF are congruent. By the
, the measure of angle ABC is equal to the measure of angle DEF, and the measure of angle GHI is equal to the measure of angle DEF. By the substitution property, the measure of angle ABC is equal to

Answer 1

Fill the blanks and finish the proof:

1. Given: ∠ABC ≅ ∠DEF and ∠GHI ≅ ∠DEF.
2. By the definition of congruent angles, m∠ABC = m∠DEF and m∠GHI = m∠DEF.
3. By substitution (or the transitive property of equality), m∠ABC = m∠GHI.

Therefore m∠ABC = m∠GHI.