Question

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Answer 1

easy proof by contradiction

Answer 2

huh

Answer 3

Assume they are not parallel and then arrive at a contradiction.

Answer 4

Suppose you have two distinct lines that are perpendicular to a given line. assume that the two lines are not parallel. then eventually they will touch forming a triangle. But this triangle will have two right angles (since the two lines are perpendicular to the given line). But a triangle can't have two right angles...this is a contradiction. Thus the lines must be parallel.