Prove the second case of the Congruent Supplements Theorem where two angles are supplementary to congruent angles. Given: <1 and <2...

Prove the second case of the Congruent Supplements Theorem where two angles are supplementary to congruent angles.

Given: <1 and <2 are supplements; 

             <3 and <4 are supplements;

             <1 congruent <4

Prove: <2 congruent <3