# Difference between revisions of "Perpendicular"

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− | + | Being '''perpendicular''' is a property of lines in a plane. Generally, when the term is used, it refers to the definition of perpendicular in [[Euclidean]] geometry. | |

+ | ==Definition== | ||

Two [[line]]s <math>l</math> and <math>m</math> are said to be '''perpendicular''' if they intersect in [[right angle]]s. We denote this relationship by <math>l \perp m</math>. In the [[Cartesian coordinate system]], a line with [[slope]] <math>m</math> is perpendicular to every line with slope <math>-\frac{1}{m}</math> and no others. | Two [[line]]s <math>l</math> and <math>m</math> are said to be '''perpendicular''' if they intersect in [[right angle]]s. We denote this relationship by <math>l \perp m</math>. In the [[Cartesian coordinate system]], a line with [[slope]] <math>m</math> is perpendicular to every line with slope <math>-\frac{1}{m}</math> and no others. | ||

− | + | ===For non-linear objects=== | |

One can also discuss perpendicularity of other objects. If a line <math>l</math> intersects a plane <math>P</math> at a point <math>A</math>, we say that <math>l \perp P</math> if and only if for ''every'' line <math>m</math> in <math>P</math> passing through <math>A</math>, <math>l \perp m</math>. | One can also discuss perpendicularity of other objects. If a line <math>l</math> intersects a plane <math>P</math> at a point <math>A</math>, we say that <math>l \perp P</math> if and only if for ''every'' line <math>m</math> in <math>P</math> passing through <math>A</math>, <math>l \perp m</math>. | ||

If a plane <math>P</math> intersects another plane <math>Q</math> in a line <math>k</math>, we say that <math>P \perp Q</math> if and only if: | If a plane <math>P</math> intersects another plane <math>Q</math> in a line <math>k</math>, we say that <math>P \perp Q</math> if and only if: | ||

for line <math>l \in P</math> and <math>m \in Q</math> passing through <math>A \in k</math>, <math>l \perp k</math> and <math>m \perp k</math> implies <math>l \perp m</math>. | for line <math>l \in P</math> and <math>m \in Q</math> passing through <math>A \in k</math>, <math>l \perp k</math> and <math>m \perp k</math> implies <math>l \perp m</math>. | ||

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+ | ==Coordinate Plane== | ||

+ | Two linear graphs in the Cartesian coordinate plane are perpendicular if and only if one's slope is the negative reciprocal of the other's. This means that their slopes must have a product of <math>-1</math>. | ||

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+ | [[Category:Geometry]] | ||

+ | [[Category:Definition]] |

## Revision as of 14:10, 20 October 2007

Being **perpendicular** is a property of lines in a plane. Generally, when the term is used, it refers to the definition of perpendicular in Euclidean geometry.

## Definition

Two lines and are said to be **perpendicular** if they intersect in right angles. We denote this relationship by . In the Cartesian coordinate system, a line with slope is perpendicular to every line with slope and no others.

### For non-linear objects

One can also discuss perpendicularity of other objects. If a line intersects a plane at a point , we say that if and only if for *every* line in passing through , .

If a plane intersects another plane in a line , we say that if and only if: for line and passing through , and implies .

## Coordinate Plane

Two linear graphs in the Cartesian coordinate plane are perpendicular if and only if one's slope is the negative reciprocal of the other's. This means that their slopes must have a product of .