State interior angle test
Answers
The Alternate Interior Angles Theorem states that, when two parallel lines are cut by a transversal , the resulting alternate interior angles are congruent . So, in the figure below, if k∥l , then ∠2≅∠8 and ∠3≅∠5 . Proof.
Answer:
The Alternate Interior Angles Theorem states that, when two parallel lines are cut by a transversal , the resulting alternate interior angles are congruent .
So, in the figure below, if k ∥ l , then ∠ 2 ≅ ∠ 8 and ∠ 3 ≅ ∠ 5 .
Two parallel lines cut by a transversal n, with angles labeled 1 through 8
Proof.
Since k ∥ l , by the Corresponding Angles Postulate ,
∠ 1 ≅ ∠ 5 .
Therefore, by the definition of congruent angles ,
m ∠ 1 = m ∠ 5 .
Since ∠ 1 and ∠ 2 form a linear pair , they are supplementary , so
m ∠ 1 + m ∠ 2 = 180 ° .
Also, ∠ 5 and ∠ 8 are supplementary, so
m ∠ 5 + m ∠ 8 = 180 ° .
Substituting m ∠ 1 for m ∠ 5 , we get
m ∠ 1 + m ∠ 8 = 180 ° .
Subtracting m ∠ 1 from both sides, we have
m ∠ 8 = 180 ° − m ∠ 1 = m ∠ 2 .
Therefore, ∠ 2 ≅ ∠ 8 .
You can prove that ∠ 3 ≅ ∠ 5 using the same method.
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