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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.
The First Six Books with Notes - Page 22
by Euclid - 1822 - 179 pages

## The First Six Books of the Elements of Euclid, with a Commentary and ...

Euclid, Dionysius Lardner - Euclid's Elements - 1828 - 542 pages
...COR. 10. — All the internal angles of any rectilinear figure ABCDE, together with four right angles, are equal to twice as many right angles as the figure has sides. Take any point F within the figure, and draw the right, lines FA, FB, FC, FD, and F E. There are formed...

## Elements of the Geometry of Planes and Solids: With Four Plates

Ferdinand Rudolph Hassler - Geometry - 1828 - 180 pages
...angles, as AGD, GDE, and so on, standing in equal segments, are equal to one another; and their sum being equal to twice as many right angles as the figure has sides wanting four: that is, eight right angles, each of these angles of the hexagon is equal eight sixths...

## A London Encyclopaedia, Or Universal Dictionary of Science, Art ..., Volume 10

Thomas Curtis - Aeronautics - 1829 - 814 pages
...twice as 118 119 липу right angles as the figure has sides. Hence the interior angles of the figure are equal to twice as many right angles as the figure has sides wanting four right angles. Cor. 1. All the interior angles of a quadrilateral figure are together equal...

## Elements of Geometry: Being Chiefly a Selection from Playfair's Geometry

John Playfair - Geometry - 1829 - 210 pages
...to all the angles of the figure, together with four right angles: that is, the angles of the figure are equal to twice as many right angles as the figure has sides, wanting four. Therefore, all the interior angles &.<•QED Com. All the interior angles of any quadrilateral...

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

Pierce Morton - Geometry - 1830 - 584 pages
...is equal to two right angles (2.) ; all the interior angles, together with all the exterior angles, are equal to twice as many right angles as the figure has angles. But all the exterior angles are, by the former part of the proposition, equal to four right...

## The Elements of geometry [Euclid book 1-3] in general terms, with notes &c ...

Euclides - 1833 - 304 pages
...= to two right angles, (prop. 13.) Therefore, all the external angles, with all the internal, are = to twice as many right angles as the figure has sides ; but the internal angles, with four right angles, are = to twice as many right angles as the figure has sides; take away from...

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

Thomas Perronet Thompson - Euclid's Elements - 1833 - 168 pages
...demonstrated. COR. 1 . All the interior angles of any plane rectilinear figure that incloses a space, are equal to twice as many right angles as the figure has sides, diminished by four right angles. For First; if the figure is one, as ABCDE, that can be divided into...

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

Euclid - Euclid's Elements - 1833 - 216 pages
...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. For...