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Therefore all the angles of the figure, together with four right angles, are equal to twice as many right angles as the figure has sides.
Euclid's Elements of Geometry: The First Six, the Eleventh and Twelfth Books - Page 56
by Euclid - 1765 - 464 pages

## The First Six Books of the Elements of Euclid: With Notes

Euclid - Euclid's Elements - 1833 - 183 pages
...(1): but the angles at the point F are equal to four right angles (2); and therefore the angles of the figure, together with four right angles, are equal to twice as many right angles as the figure has sides. Cor. 7. The external angles of any rectilineal figure are together equal to four right angles....

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

Thomas Perronet Thompson - Euclid's Elements - 1833 - 150 pages
...isf equal to two right angles ; all the interior together with all the exterior angles of the figure, are equal to twice as many right angles as the figure has sides. But (by Cor. 1 .) all the interior angles are together equal to twice as many right angles as...

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

Euclid - 1835 - 513 pages
...angles. Wherefore, " if a side of a triangle," &c. QED COR. 1. All the interior angles of any rectilineal figure, together with four right angles, are equal to twice as many right angles as the figure has sides. For any rectilineal figure ABCDE can be divided into as many triangles as the figure has sides,...

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

Mathematics - 1835
...angles of any rectilineal figure are together equal to four right angles : and all the interior angles, together with four right angles, are equal to twice as many right angles as the figure has sides. For, if from any point in the same plane, straight lines be drawn, one after the other, parallel...

## The Element of Geometry

John Playfair - Geometry - 1836 - 114 pages
...equal to two right angles. Which was to be proved. COR. I. All the interior angles of any rectilineal figure, together with four right angles, are equal to twice as many right angles as the figure has sides. For any rectilineal figure ABCDE can be divided into as many triangles as the figure has sides,...

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

Mathematics - 1836 - 472 pages
...triangle are equal to two right angles. Сон. 1. All the interior angles of any rectilineal figure are equal to twice as many right angles as the figure has sides, wanting four right anglesť 2. All the exterior angles of any rectilineal figure are to. gether...

## Elements of Plane Geometry According to Euclid

Andrew Bell - Euclid's Elements - 1837 - 240 pages
...triangles ; that is (1. 15, Cor. 2), together with four right angles. Therefore all the angles of the figure, together with four right angles, are equal to twice as many right angles as the figure has sides. Let the sum of the interior angles be denoted by I, the number of sides by n, and a right angle...

## The First Six and the Eleventh and Twelfth Books of Euclid's Elements: With ...

Euclid, James Thomson - Geometry - 1837 - 390 pages
...equal to two right angles. Wherefore, if a side, &c. Cor. 1. All the interior angles of any rectilineal figure, together with four right angles, are equal to twice as many right angles as the figure has sides. For any rectilineal figure ABCDE can be divided into as many triangles as the figure has sides,...