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

Robert Simson - Trigonometry - 1762 - 466 pages
...adjacent angles. but when the adjacent angles which one ftraight line makes with another ftraight line are e.qual to one another, each of them is called a right ,* angle ; therefore Def each of the angles DCF, ECF is a right angle. wherefore from the given point C in the...

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

Robert Simson - Trigonometry - 1775 - 520 pages
...to the angle CHG; and they are adjacent angles ; but when a ftraight line ftanding cet on a ftraight line makes the adjacent angles equal to one another, each of them is a right angle, and the ftraight line which flands upon the other is called a perpendicular to it; therefore...

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

Robert Simson - Trigonometry - 1781 - 466 pages
...the angle CHG; and they are adjacentc. 8. i. angles. but when a ftraight line ftanding on a ftraight line makes the adjacent angles equal to one another, each of them is aright angle, and the ftraight linewhich ftands upon the other is called a perpendiculartoit. therefore...

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

John Playfair - Euclid's Elements - 1795 - 444 pages
...to the 111 .le CKG ; and they are adjacent angles; but when a ftraight line ftanding on a ftraight line makes the adjacent angles equal to one another, each of them is a right angle, and the flraight line which ftands upon the other is called a perpendicular to it ;...

## The Elements of Euclid: Viz. the First Six Books, with the Eleventh and ...

Alexander Ingram - Trigonometry - 1799 - 351 pages
...to the angle , CHG ; and they are adjacent angles ; but when a ftraight line ftanding on a ftraight line makes the adjacent angles equal to one another, each of them is a right angle, and the ftraight line which ftands upon the other, is called a perpendicular to it ;...

## The Elements of Euclid: Also the Book of Euclid's Data ...cor. viz. The ...

Robert Simson - Trigonometry - 1804
...angle CHG; and they are adjacent e. 8. i. :angles. but when a ftraight line flanding on a ftraight line makes the adjacent angles equal to one another, each of them is a right angle, and the ftraight line which ftands upon the other is called af perpen- f. to.Def.t....

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

John Playfair - Euclid's Elements - 1804 - 470 pages
...therefore the angle AFE is equal b to the angle BFE. And when a ftraight line flanding upon another makes the adjacent angles equal to one another, each of them is a right c angle : Therefore each of the angles AFE, BFE is a right angle; wherefore the ftraight line...

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

John Playfair - Euclid's Elements - 1806 - 320 pages
...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 other is called a perpendicular...