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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: Containing the First Six Books of Euclid: With a ... - Page 18
by John Playfair - 1819 - 317 pages

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

Robert Potts - 1865 - 528 pages
...15.) therefore the angle FHC is equal to the angle GHC; (i. 8.) and these are adjacent angles. But when a straight line standing on another straight...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...

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

Euclides - 1865 - 80 pages
...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...

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

Euclides - 1865 - 402 pages
...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 angle ; (i. def. 10) therefore each of the angles AFE, BFE, is a right angle; wherefore...

## 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
...two straight lines to one another, which meet together, but are not in the same straight line. 10. When a straight line standing on another straight...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 - 424 pages
...[Definition 24. therefore the angle DCF is equal to the angle ECF; [I. 8. and they are adjacent angles. But when a straight line, standing on another straight...another, each of the angles is called a right angle ; ' [Definition 10. therefore each of the angles DCF, ECF is a right angle. Wherefore/row the given...

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

Isaac Todhunter - Euclid's Elements - 1867 - 426 pages
...from the centre G ; [I. Definition 15. therefore the angle ADG is equal to the angle BDG. [I. 8. But when a straight line, standing on another straight...adjacent angles equal to one another, each of the angle's is called "a right angle ; [I. Definition 10. therefore the angle BDG is a right angle. But...

## 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...