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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

## Geometry, Plane, Solid, and Spherical, in Six Books: To which is Added, in ...

Pierce Morton - Geometry - 1830 - 584 pages
...the dihedral angle CABE. 5. When one plane standing upon another plane makes the adjacent dihedral angles equal to one another, each of them is called a right dihedral angle ; and the plane which stands upon the other is said to be perpendicular (or at right...

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

John Playfair - Euclid's Elements - 1832 - 358 pages
...: therefore the angle ADG is equal (8. 1.) to the angle GDB: But when a straight line standing upon another straight line makes the adjacent angles equal to one another, each /• jii • • i j_ 1 / rr J f* i \ of the angles is a right angle (7. def. 1.) Therefore the aniile...

## Geometry Without Axioms; Or the First Book of Euclid's Elements. With ...

Thomas Perronet Thompson - Euclid's Elements - 1833 - 168 pages
...not expressed, it is always the direct angle that is meant. XXXVII. 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...

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

Euclides - 1834 - 518 pages
...base EB ; therefore the angle AFE is equal* to the angle BFE : 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; therefore each of the angles AFE, BFE is a right angle : wherefore the straight line...

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

Euclid - 1835 - 540 pages
...centre G * : Therefore the angle ADG is equal0 to the angle GDB : But when a straight line standing upon another straight line makes the adjacent angles equal to one another, each of the angles is a right angle :d Therefore the angle GDB is a right angle: But FDB is likewise a right...

## Library of Useful Knowledge: Geometry plane, solid, and spherical [by Pierce ...

Mathematics - 1835 - 684 pages
...the dihedral angle CABE. 5. When one plane standing upon another plane makes the adjacent dihedral angles equal to one another, each of them is called a right dihedral angle ; and the plane which stands upon the other is said to be perpendicular (or at right...

## The Teacher's Assistant in the "Course of Mathematics Adapted to the Method ...

Mathematics - 1836 - 488 pages
...another, which meet together but are not in the same straight line. 7. 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...

## The Element of Geometry

John Playfair - Geometry - 1836 - 148 pages
...therefore the angle ADG is equal (7. 1.) to the angle BDG ; but when a straight line standing upon another straight line, makes the adjacent angles equal to one another, each of the angles is a right angle (Def. 27. 1.); therefore BDG is a right angle ; but BDF is likewise a right...