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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

## 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...

## 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...

## 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 - 80 pages
...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...

## Loftus's Inland Revenue Officers' Manual ...

William Harris Johnston - 1865 - 478 pages
...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 - 172 pages
...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 ...

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...

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

Robert Potts - 1868 - 434 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...