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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.
The Elements of geometry; or, The first six books, with the eleventh and ... - Page 2
by Euclides - 1855

## Appleton's Cyclopędia of Drawing: Designed as a Textbook for the Mechanic ...

William Ezra Worthen - Architectural drawing - 1857 - 410 pages
...lines, AB, GB, is named the angle ABC, or CBA ; but if there be only one angle at a point, it may be expressed by a letter placed at that point ; as the angle at E.' When a straight line standing on another straight line makes the adjacent angles equal to one another,...

## Elements of Geometry and Conic Sections

Elias Loomis - Conic sections - 1858 - 234 pages
...the angle ECD is the difference between the two angles BCD, BCE. 10. When a straight line, meeting another straight line, makes the adjacent angles equal to one another, each of them is called a right angle, and the straight line which meets the other is called a perpendicular...

## The popular educator, Volume 3

Popular educator - 1860
...equal to the base OH, and the angle CHF (I. 4) to the angle CBO ; and they are adjacent angles. But when a straight line standing on another straight...the adjacent angles equal to one another, each of them is a right angle, and the straight line which stands upon the other is called a perpendicular...

## Euclid's Elements of Geometry: Chiefly from the Text of Dr. Simson, with ...

Robert Potts - Geometry, Plane - 1860 - 361 pages
...together, but are not in the same straight line. NB If there be only one angle at a point, it may be expressed by a letter placed at that point, as the angle at E ; but when several angles are at one point B, either of them is expressed by three letters, of which...

## A course of geometrical drawing

William Schofield Binns - 1861
...inclination of two straight lines to one another, meeting or cutting each other in a point, as c (10) " When a straight line standing on another straight...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...

## A handbook of practical gauging

Janes Boddely Keene - 1861
...the angle. Plate I., Fig. 1. 10. Angles are of three kinds. Fig. 2. a. The Right Angle. — If one straight line standing on another straight line makes the adjacent angles equal to one another, each is .called a right angle, and the line standing on the other is said to be perpendicular to it. b....

## Euclid's Elements of geometry, books i. ii. iii. iv

Euclides - 1862 - 140 pages
...two straight lines to one another, which meet together, but are not in the same straight line. 10. When a straight line standing on another straight...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...

## The school Euclid: comprising the first four books, by A.K. Isbister

Euclides - 1862
...by DB, CB, is called the angle DEC, or CBD ; but, if rhere be only one angle at a point, it may be expressed by a letter placed at that point : as the angle at E.' X. When a straight line standing on another straight line makes the adjacent angles equal to one another,...