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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.
Descriptive Astronomy - Page 795
by George Frederick Chambers - 1867 - 816 pages

## Elements of Geometry: Containing the First Six Books of Euclid, with a ...

John Playfair - 1806 - 320 pages
...angle at a point, it may be expressed ' by a letter placed at that point ; as the angle at E.' VII. 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...

## Pantologia. A new (cabinet) cyclopædia, by J.M. Good, O. Gregory ..., Volume 5

John Mason Good - 1813 - 714 pages
...two straight lines to or.e 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 the angles is called a right angle; and the straight line which stands on the...

## The Elements of Euclid; viz. the first six books, together with the eleventh ...

Euclides - 1814 - 560 pages
...one angle at a point, it may be ex' pressed by a letter placed at that point; as the angle at E.' X. 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...

## Elements of Geometry: Containing the First Six Books of Euclid: With a ...

John Playfair - 1819 - 354 pages
...one angle at a point, it may be expressed by a letter placed at that point ; as the angle at E.' VII. 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...

## Elementary Illustrations of the Celestial Mechanics of Laplace: Part the ...

Pierre Simon marquis de Laplace, Thomas Young - 1821 - 402 pages
...described by three letters placed near the lilies, the middle letter at the angular point % 64. DEFINITION. When a straight line standing on another straight line makes the adjacent angles equal, they are called right angles. 65. DEFINITION. A straight line between two right angles is called a...

## Elements of Geometry and Trigonometry: With Notes

Adrien Marie Legendre - 1822 - 394 pages
...When a straight line AB meets another straight line CD, so as to make the adjacent angles BAC, BAD equal to each other, each of those angles is called a right angle ; and the line AB is said to be perpendicular to c CD. XI. Every angle BAC, less than D\ a right angle,...

## A Popular Course of Pure and Mixed Mathematics ...: With Tables of ...

Peter Nicholson - 1825 - 1046 pages
...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 another, each of the angles is called a right angle ; and the straight line which stands on the...

## The Elements of Euclid: The Errors by which Theon, Or Others, Have Long ...

Robert Simson - 1827 - 546 pages
...one angle at a point, it may be expressed ' by a letter placed at that point : as the angle at E.' X. 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...