Right angle (geometry): Difference between revisions
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imported>Ro Thorpe (added a bit that I'd been thinking of) |
imported>Miguel Adérito Trigueira (added missing part of demonstration, sp) |
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[[Image:Right angle (geometry) definition.png|frame|Diagram showing the definition of a right angle. The green parts are not part of the construction but show that the angles are both 90 degrees and equal to one another]] | [[Image:Right angle (geometry) definition.png|frame|Diagram showing the definition of a right angle. The green parts are not part of the construction but show that the angles are both 90 degrees and equal to one another]] | ||
In [[Euclidean geometry]], a '''right angle''', | In [[Euclidean geometry]], a '''right angle''', symbolized by the L-shaped figure '''∟''', is created when two straight lines meet perpendicularly at 90 degrees to each other. The plus sign, +, consists of two such lines, and so the four angles at its heart are all right angles. | ||
The right angle bisects the angle of the line into two equal parts. | The right angle bisects the angle of the line into two equal parts. | ||
| Line 7: | Line 7: | ||
The right angle is demonstrated: | The right angle is demonstrated: | ||
:Given a line DC with point B lying on it | :Given a line DC with point B lying on it | ||
:Project a line from B through point A | |||
:Take B as the vertex of angle ABC | :Take B as the vertex of angle ABC | ||
:If the angle ABC equals the angle ABD | :If the angle ABC equals the angle ABD | ||
:then angle ABC is a right angle, | :then angle ABC is a right angle, | ||
:and so is angle ABD | :and so is angle ABD | ||
Revision as of 05:58, 18 August 2008
_definition.png)
Diagram showing the definition of a right angle. The green parts are not part of the construction but show that the angles are both 90 degrees and equal to one another
In Euclidean geometry, a right angle, symbolized by the L-shaped figure ∟, is created when two straight lines meet perpendicularly at 90 degrees to each other. The plus sign, +, consists of two such lines, and so the four angles at its heart are all right angles.
The right angle bisects the angle of the line into two equal parts.
The right angle is demonstrated:
- Given a line DC with point B lying on it
- Project a line from B through point A
- Take B as the vertex of angle ABC
- If the angle ABC equals the angle ABD
- then angle ABC is a right angle,
- and so is angle ABD