Video

Parallel & perpendicular lines (Full video)

Khan Academy

Description: Parallel lines are lines in a plane that are always the same distance apart. Parallel lines never intersect. Perpendicular lines are lines that intersect at a right (90 degrees) angle. Created by Sal Khan and Monterey Institute for Technology and Education. Identify all sets of parallel and perpendicular lines in the image below. It looks like two lines won't intersect, but you can't just always assume based on how it looks. You really have to have some information given in the diagram or the problem that tells you that they are definitely parallel, that they're definitely never going to intersect.

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