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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 - 1857 - 226 pages

## The school edition. Euclid's Elements of geometry, the first six books, by R ...

Euclides - 1864 - 448 pages
...which is contained by lOB, CB, is called the angle DBC, or CBD. X. When a straight 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 the other is called a...

## The College Euclid: Comprising the First Six and the Parts of the Eleventh ...

Euclides - 1865 - 402 pages
...equal to the angle ECF; (i. 8) 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 the angles is called a right angle ;' (def. 10) therefore each of the angles DCF, ECF, is a right angle....

## Elements of plane geometry, book i, containing nearly the same propositions ...

Euclides - 1865
...its sides. 9. When a straight line standing on another straight line makes the adjacent angles equal, each of them is called a RIGHT ANGLE; and the straight line which stands upon the other is called a PERPENDICULAR to it. 10. An OBTUSE ANGLE is that which is greater...

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

Robert Potts - 1865 - 528 pages
...that which is contained by DB, CB, is called the angle DBC, or CBD, When a straight 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 liae which stands on the other ia called a...

## Loftus's Inland Revenue Officers' Manual: a guide to the duties and ...

William Harris JOHNSTON - 1865
...other angle between them, such as the angles ВАС and DA 0. When one straight line standing upon another straight line makes the adjacent angles equal to one another, each such angle is called a right angle, and either of the straight lines is said to be a perpendicular...

## An English primer; compiled under the superintendence of E.C. Lowe

Edward Clarke Lowe - 1866
...another, which meet together, but are not in the same straight line. 10. When a straight 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 the other is & perpendicular...

## The Elements of Euclid for the Use of Schools and Colleges: Comprising the ...

Euclid, Isaac Todhunter - Euclid's Elements - 1867 - 426 pages
...equal to the angle ECF; [I. 8. 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 the angles is called a right angle ; [Definition 10. therefore each of the angles DCF, ECF is a right...

## Modern Methods in Elementary Geometry

E. M. Reynolds - Geometry - 1868 - 112 pages
...When an angle stands alone one letter only is often used, as A. When one straight 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 the other is said to be...