How Are The Alternate Interior Angles Theorem And The Alternate Exterior Angles Theorem Different. Exterior angles are also created by a transversal line crossing 2 straight lines. Also like with interior angles the above exterior angles are equal when a transversal line crosses 2 parallel lines.
So in the figure below if k l then. The angle in a semicircle is 90. So that means that angles 1 and 8 are congruent or the same and angles 2 and 7 are congruent as well.
Alternate exterior angles are created in the space outside the parallel lines on alternating sides.
The alternate interior angles theorem states that the alternate interior angles are congruent when the transversal intersects two parallel lines. By our previous proposition all right angles are congruent so the Alternate Interior Angle Theorem applies. Alternate interior angles are equal if the lines intersected by the transversal are parallel. Interior alternating angles and exterior alternating angles are congruent that is they have the same measure of the angle.