# Perpendicular straight lines

From Encyclopedia of Mathematics

Straight lines forming a right angle with each other (such straight lines need not intersect in space). A straight line $l$ and a plane $\alpha$ are said to be mutually perpendicular if $l$ is perpendicular to any straight line lying in $\alpha$. See Orthogonality for a generalization of the concept of perpendicularity.

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Perpendicular straight lines.

*Encyclopedia of Mathematics.*URL: http://www.encyclopediaofmath.org/index.php?title=Perpendicular_straight_lines&oldid=31464