straightedge n : hand tool consisting of a flat rigid rectangular bar (metal or wood) that can be used to draw straight lines (or test their straightness)
- Living one's life against/without the use of alcohol, smoking, and illegal drugs.
- For the subculture, see Straight edge.
A straightedge is a tool similar to a ruler, but without markings.
Compass-and-straightedge constructionAn idealized straightedge is used in compass-and-straightedge constructions in plane geometry. It may be used:
- Given two points, to draw the line connecting them.
- Given a point and a circle, to draw either tangent.
- Given two circles, to draw any of their common tangents.
It is possible to do all compass and straightedge constructions without the straightedge. That is, it is possible, using only a compass, to find the intersection of two lines given two points on each, and to find the tangent points to circles. It is not, however, possible to do all constructions using only a straightedge. It is possible to do them with straightedge alone given one circle and its center.
- Wayne R. Moore, Foundations of Mechanical Accuracy, Moore Special Tool Company, Bridgeport, CT (1970)
straightedge in German: Haarlineal
straightedge in Persian: ستاره (ریاضی)
straightedge in Swedish: Rätskiva