# Geometry

Give an indirect proof of the theorem.

1. If two lines are parallel to a third line then they are parallel to each other

2. Solve the equation S=(n-2) 180 degrees for n when S is a given value. Find the number of sides of the polygon ( if possible) if the given value corresponds to the number of degrees in the sum of the interior angles of a polygon.

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#### Solution Preview

(1) Let the two lines be AB and CD, and let the third line be EF.

Given: AB || EF and CD || EF

To Prove: AB || CD

Proof: If possible, assume that AB and CD are not ...

#### Solution Summary

The expert gives an indirect proof of the theorem. Neat, step-by-step solution is provided.

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