# Interior Angle Sum

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• Sep 26th 2010, 09:23 PM
MATNTRNG
Interior Angle Sum
If l1 and l2 are lines are lines on the plane such that they are parallel transports along a transversal l, then they are parallel transports along any transversal.

Use the above theorem to prove that the interior angle sum of a triangle is 180.
• Sep 26th 2010, 11:36 PM
Prove It
http://i22.photobucket.com/albums/b3...oftriangle.jpg

The angles marked $\alpha^{\circ}$ are equal because they are alternate (Z) angles.

The angles marked $\gamma^{\circ}$ are equal because they are alternate (Z) angles.