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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 and Conic Sections - Page 10
by Elias Loomis - 1849 - 226 pages

Mensuration of lines, areas, surfaces, and volumes

Robert Rawson - 1856
...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, each of the angles is called a right angle ; and the straight line which stands on the other is called a perpendicular...

APPLETONS' CYCLOPAEDIA OF DRAWING

W.E. WORTHEN - 1857 - 600 pages
...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, each of the angles is called a right angle; and the straight lines are said to be perpendicular to each other...

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

William Ezra Worthen - Architectural drawing - 1857 - 410 pages
...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, each of the angles is called a rig fit angle ; and the straight lines are said to be perpendicular to each...

The popular educator, Volume 3

Popular educator - 1860
...angle CHF (I. 4) to the angle CBO ; and they are adjacent angles. But when a straight line standing on another straight line makes 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 (l)'f. 10)...

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

Robert Potts - Geometry, Plane - 1860 - 361 pages
...therefore the angle ADG is equal to the angle GDB : (I. 8.) but when a straight line standing upon another straight line makes the adjacent angles equal to one another, each of the angles is a right angle ; (I. def. 10.) therefore the angle GDB is a right angle : but FDB is likewise...

A course of geometrical drawing

William Schofield Binns - 1861
...one another, meeting or cutting each other in a point, as c (10) " 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...

A handbook of practical gauging

Janes Boddely Keene - 1861
...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....

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

Euclides - 1862
...therefore the angle AFE is equal to the angle BFE ; (i. 8) but 'when a straight line standing upon another straight line makes the adjacent angles equal to one another, each of them is a right anele ;' therefore each of the angles AFE, BFE, is a right angle; wherefore the straight line...