Question

What is the missing step in this proof?

Answer 1

The answer is the third choice..
Statement: Angle 1 and angle 4 are congruent, and angle 3 and angle 5 are congruent.
Reason: Alternate Interior Angles Theorem

Hope this helps!

Answer 2

Answer:

(C)

Step-by-step explanation:

Given: The ΔABC.

To prove: the sum of interior angles measures of ΔABC is 180°.

Proof:

Statement                                                            Reason

1. Let points A, B and C form a triangle             given

2. Let DE be a line passing       Defining a parallel line and labeling angles

through B and parallel to AC

with angles as labelled.

3. ∠1≅∠4 and ∠3≅∠5                Alternate interior angles theorem

4. m∠1=m∠4 and m∠3=m∠5    Congruent angles have equal measures

5.m∠4+m∠2+m∠5=180°         Angle addition and definition of straight line

6.m∠1+m∠2+m∠3=180°            Substitution

Hence proved

hence, option C is correct