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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

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

Euclid, Isaac Todhunter - Euclid's Elements - 1883 - 428 pages
...angle AFE is equal to the angle BFE. [I. 8. 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 ; [I. Definition 10. therefore each of the angles AFE, BFE is a right angle. Therefore the straight...

## Geometry for schools, comprising books i. and ii. of Euclid, with some ...

Euclides - 1883 - 176 pages
...L DCF = L ECF, and these 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. .-. CF is at right angles to AB, and is drawn from the given point CQEF NSte.— Since an angle may...

## Stewart's specific subjects. Euclid. [1st] (-3rd stage). [With 2 issues of ...

Stewart W. and co - 1884 - 272 pages
...named from three or one letters, as ABC or B. X. When a straight line standing on another straight line makes the adjacent angles equal to one another,...and the straight line which stands on the other is _ called a perpendicular to it. XI. An obtuse angle is greater than a right angle. XII. An acute angle...

## The Elements of Euclid, books i. to vi., with deductions, appendices and ...

Euclides - 1884 - 434 pages
...a straight line stands on another straight line, and makes the adjacent angles equal to each other, each of the angles is called a right angle ; and the...stands on the other is called a perpendicular to it. CUD Thus, if AB stands on CD in such a manner that the adjacent angles ABC, ABD are equal to one another,...

## The text of Euclid's geometry, book 1, uniformly and systematically arranged ...

Euclides - 1884 - 214 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...stands on the other is called a perpendicular to it. PROPOSITION XIII. THEOREM. The angles which one straight line makes with another straight line on one...

## An introduction to geometry, consisting of Euclid's Elements, book ..., Volume 1

Euclides - 1884 - 182 pages
...line standing on another straight line makes the adjacent angles equal to each other, each of these angles is called a right angle; and the straight line...stands on the other is called a perpendicular to it. 11. An obtuse angle is that which is greater than a right angle. 12. An acute angle is that which is...

## Mathematical Questions with Their Solutions: From the ..., Volumes 40-42

1884 - 434 pages
...bine 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...stands on the other is called a perpendicular to it." Let us then take two sets of such lines and apply one to tjie other, so that the feet of the perpendiculars...

## Littell's Living Age, Volume 161

American periodicals - 1884 - 862 pages
...same straight line [plane]. X. When a straight line [plane] standing on another straight line [plane] makes the adjacent angles equal to one another, each of the angles is called a right angle [right dihedral angle]. XV. A circle [cone of revolution with vertex at the eye] is a figure contained...