Q:
# What Are Perpendicular Lines?

**Perpendicular lines are those that form a right angle at the point at which they intersect.** Parallel lines, though in the same plane, never intersect.

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Another fact about perpendicular lines is that their slopes are negative reciprocals of one another. The two slopes multiplied together always produce an answer of -1. The formula for slope is rise divided by run. If a line goes through point (x1y1) and point (x2y2), the formula for its slope is set up as y2 - y1 / x2 - x1. If the slope of one of the two perpendicular lines is 1/2, the slope of the other is -2.

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