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When a straight line standing on another straight line makes the adjacent angles equal to one another, each of the angles is called a right angle; and the straight line which stands on the other is called a perpendicular to it.
Elements of geometry, based on Euclid, book i - Page 23
by Edward Atkins - 1877

## A Commentary on the First Book of Euclid's Elements

Proclus - Mathematics - 1992 - 432 pages
...primacy over the things that are plural and separated. X-XII. When a straight line set up on a straight line makes the adjacent angles equal to one another, each of the equal angles is a right angle and the straight line standing on the other is called a perpendicular...

## The Poincaré Half-plane: A Gateway to Modern Geometry

Saul Stahl - Geometry, Non-Euclidean - 1993 - 320 pages
...that Euclid felt the need to acknowledge their efforts. 10. When a straight line set up on a straight line makes the adjacent angles equal to one another, each of the equal angles is right, and the straight line standing on the other is called a perpendicular to that...

## Mathematics: The Science of Patterns: The Search for Order in Life, Mind and ...

Keith Devlin - Mathematics - 1996 - 228 pages
...lies evenly with the points on itself. Definition 10 When a straight line standing on another straight line makes the adjacent angles equal to one another, each of the equal angles is right and the straight line standing on the other is called a perpendicular to that...

## Foundations and Fundamental Concepts of Mathematics

Howard Whitley Eves - Mathematics - 1997 - 370 pages
...straight lines, the angle is called a rectilinear angle. 10. When a straight line erected on a straight line makes the adjacent angles equal to one another, each of the equal angles is called a right angle, and the straight line standing on the other is called a perpendicular...

## Geometry: Plane and Fancy

David A. Singer - Mathematics - 1998 - 176 pages
...know about right angles. Euclid's tenth definition says: When a straight line set up on a straight line makes the adjacent angles equal to one another, each of the equal angles is right, and the straight line standing on the other is called a perpendicular to that...

## Space from Zeno to Einstein: Classic Readings with a Contemporary Commentary

Nick Huggett - Philosophy - 1999 - 292 pages
...angle are straight, the angle is called rectilineal. 10. When a straight line set up on a straight line makes the adjacent angles equal to one another, each of the equal angles is right, and the straight line standing on the other is called a perpendicular to that...

## Mathematical Expeditions: Chronicles by the Explorers

Reinhard Laubenbacher, David Pengelley - Mathematics - 2000 - 292 pages
...postulate itself. Euclid, from Elements BOOK I. DEFINITION 10. When a straight line set up on a straight line makes the adjacent angles equal to one another, each of the equal angles is right, and the straight line standing on the other is called a perpendicular to that...

## A Course in Modern Geometries

Judith Cederberg - Mathematics - 2004 - 472 pages
...angle are straight, the angle is called rectilineal. 10. When a straight line set up on a straight line makes the adjacent angles equal to one another, each of the equal angles is right, and Reprinted with permission of Cambridge University Press from The Thirteen...

## A Mathematics Sampler: Topics for the Liberal Arts

William P. Berlinghoff, Kerry E. Grant, Dale Skrien - Mathematics - 2001 - 672 pages
...familiar figures in more or less familiar ways. For example: « When a straight line crossing a straight line makes the adjacent angles equal to one another, each of the equal angles is called a right angle, and the straight line crossing the other is called a perpendicular...

## The Sheet-Metal Worker's Instructor

R. H. Warn, John G. Horner - Crafts & Hobbies - 2002 - 292 pages
...straight liue, B, makes the adjacent angles equal to one another, each of B Fig. 1. Fig. 2. the angles Ls called a right angle, and the straight line which...stands on the other is called a perpendicular to it (Fig. 2). 8. An obtuse angle is that which is greater than a right angle (Fig. 3). 9- An acute angle...