Alternate Interior Angles Theorem Proof Calculator

Prove Parallelism Using Alternate Interior Angles

Enter the measure of the first alternate interior angle.
Enter the measure of the second alternate interior angle.

Explore the Alternate Interior Angles Theorem with our interactive calculator. Input two alternate interior angle measurements to instantly determine if the lines intersected by a transversal are parallel. Understand this fundamental geometry concept and verify angle equality for proofs and problem-solving.

Formula:

The Alternate Interior Angles Theorem states that if two parallel lines are cut by a transversal, then the alternate interior angles are equal. Conversely, if the alternate interior angles formed by two lines and a transversal are equal, then the lines are parallel. This calculator helps you verify this principle:

If ∠A and ∠B are alternate interior angles, then:
If ∠A = ∠B, the lines are parallel.
If ∠A ≠ ∠B, the lines are not parallel.

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