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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

## Plane Trigonometry ...

Isaac Todhunter - 1860 - 318 pages
...meet together, but are not in the same straight line. And when a straight line standing on another makes the adjacent angles equal to one another, each of the angles is called a right angle. A right angle is divided into 90 equal parts called degrees, a degree is divided into 60 equal parts...

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

Robert Potts - Geometry, Plane - 1860 - 380 pages
...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 right...

## A course of geometrical drawing

William Schofield Binns - 1861 - 238 pages
...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,...stands on the other is called a perpendicular to it." The angles AB c, ABD, are right angles. Obs. 1. Because DB is in the same straight line with B c, the...

## Euclid's plane geometry, books iii.-vi., practically applied; or, Gradations ...

Euclides - 1861 - 464 pages
...st. line makes the adj. ¿_s equal to each other, each of these /.s is called a rt. ¿_ ; and the st. line which stands on the other is called a perpendicular to it. Ax. 1. Things which are equal to the same thing are equal to one another. EI 2 CI 2 Dat. Quass. Pst....

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

Euclides - 1862 - 140 pages
...ECF; (I. 8.) And they are adjacent angles. 5. But 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; (def. 10.) 6. Therefore each of the angles DCF, ECF, is a right angle. Conclusion. — Therefore from...

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

Euclides - 1862 - 172 pages
...ADG must be equal to the angle GDB ; (L, 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 must be a right angle ; but FOB is a right angle;...

## Euclid's plane geometry, practically applied; book i, with explanatory notes ...

Euclides - 1863 - 74 pages
...line makes the adjacent angles equal to each other, each of these angles is called a right angle; D and the straight line which stands on the other is called a perpendicular to it. , The Anglo CDA being equal to angle CDB, each of them is a right angle, and CD is perpendicular toAB....

## The elements of plane geometry; or, The first six books of Euclid, ed. by W ...

Euclides - 1863 - 122 pages
...line standing on another straight line makes the adjacent angles equal to one another, each of these angles is called a right angle ; and the straight line which stands on tbo other is called a perpendicular to it —!— XI. An obtuse angle is that which is greater than...