Final answer:
To prove that ∠1 is congruent to ∠3 given the lines ab and cd, we can use the property of corresponding angles. If lines ab and cd are parallel, then the alternate interior angles formed by the transversal line ac will be congruent. Therefore, ∠1 is congruent to ∠3.
Step-by-step explanation:
To prove that ∠1 is congruent to ∠3 given the lines ab and cd, we can use the property of corresponding angles.
If lines ab and cd are parallel, then the alternate interior angles formed by the transversal line ac will be congruent. Since both ∠1 and ∠3 are alternate interior angles formed by line ac, they will be congruent.
Therefore, ∠1 is congruent to ∠3.