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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 First Six Books of the Elements of Euclid: And Propositions I-XXI of ...

Euclid, John Casey - Euclid's Elements - 1885 - 340 pages
...adjacent angles at both sides of itself equal, each of the angles is called a right angle, and the line which stands on the other is called a perpendicular to it. D Hence a right angle is equal to its supplement. xv. An acute angle is one which is less than a right...

The first six books of the Elements of Euclid, and propositions i.-xxi. of ...

Euclides - 1885 - 340 pages
...adjacent angles at both sides of itself equal, each of the angles is called a right angle, and the line which stands on the other is called a perpendicular to it. Hence a right angle is equal to its supplement. xv. An acute angle is one which is less than a right...

Elementary Physiography: An Introduction to the Study of Nature

John Thornton - Physical geography - 1888 - 266 pages
...the following definition of a right angle : — ' When a straight line standing on another straight line makes the adjacent angles equal to one another,...stands on the other is called a perpendicular to it.' We find it convenient for the purposes of angular measurement to divide the right angle into smaller...

The Harpur Euclid: An Edition of Euclid's Elements

Edward Mann Langley, W. Seys Phillips - 1890 - 538 pages
...instead of it. See Note 2 on Prop. 9. DEF. 10. — 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 said to be perpendicular, or at right angles, to it. The symbol for ' perpendicular 'is x r. The student...

The Elements of Plane and Solid Geometry ...

Edward Albert Bowser - Geometry - 1890 - 414 pages
...said to bisect the angle between the non-coincident sides BA and BE. Fig. 6 Fig. 7 0 Fig. 8 O Fig. 9 called a right angle; and the straight line which stands on the other is said to be perpendicular or at right angles to it. Thus, if the adjacent angles AOC and BOC are equal...

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

Euclid - Geometry - 1892 - 460 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. Therefore CH is a perpendicular drawn to the given straight line AB from the given point C without...

Plane and Solid Geometry

James Howard Gore - Geometry - 1898 - 232 pages
...other. 35. When a straight line standing on another makes the adjacent angles equal to each other, f each of the angles is called a Right Angle; and the straight line which stands ou the other side is said to be perpendicular or at right angles to it. A_ Thus, if the adjacent angles...

Mathematics: Mechanic's bids and estimates. Mensuration for beginners. Easy ...

Seymour Eaton - 1899 - 362 pages
...standing on another straight line makes the adjacent angles equal to one another, I v/ \ GB each of these angles is called a right angle, and the straight line...stands on the other is called a perpendicular to it (Definitions). Therefore CH is a perpendicular drawn to the given straight line AB from the given point...