Question

please help me quick Complete the proof of the exterior angle theorem. Given: ∠4 is an exterior angle of △ABC. Prove: m∠1+m∠2=m∠4

Answer 1

Answer:

Step-by-step explanation:

Statement                                                                        Reason

1.∠4 is an exterior angle of ΔABC                                  Given

2.∠3 and∠4 form a linear pair                                 Linear pair theorem

3.∠3 is supplementary to ∠4                        Property of supplementary angle

4.m∠3+m∠4=180°                                        Definition of supplementary angle

5.m∠1+m∠2+m∠3=180°                               Triangle sum theorem

6.m∠1+m∠2+m∠3=m∠3+m∠4                     From step 4 and 5

7.m∠1+m∠2=m∠4                                        Subtraction rule