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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

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

Euclides - 1864 - 448 pages
...together, but are not in the same straight line. I) 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...

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

Euclides - 1865
...lines which meet in a point, called the vertex of an angle, and the two lines are called 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...

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

Robert Potts - 1865 - 528 pages
...together, but are not iii the same straight line. D XB 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...

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

Euclides - 1865 - 402 pages
...by DB, CB, is called the angle DBC, or CBD ; 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 !•'.. X. When a straight line standing on another straight line makes the adjacent angles equal to...

## 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...

## Descriptive Astronomy

George Frederick Chambers - Astronomy - 1867 - 888 pages
...lines to each other in the same plane gives rise to a plant rectilineal angle, or simply an angle. When a straight line, standing on another straight line, makes the adjacent angles equal to each other, each of those angles is called a right angle; but if the adjacent angles are not equal...

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

Euclid, Isaac Todhunter - Euclid's Elements - 1867 - 424 pages
...lines DB, CB is named the angle DBC, or CBD • 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. 10. When a straight line standing on another straight line, makes the adjacent angles equal to one...

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

Euclid, Isaac Todhunter - Euclid's Elements - 1867 - 426 pages
...lines DB, CB is named the angle DBC, or CBD ; 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. 10. When a straight line standing on another straight line, makes the adjacent angles equal to one...