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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.
A Course of Mathematics ...: Composed for the Use of the Royal Military ... - Page 64
by Charles Hutton - 1811

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

Thomas Perronet Thompson - Euclid's Elements - 1833 - 150 pages
...severally capable of being so divided. And because the interior angles of each of such smaller figures are equal to twice as many right angles as the figure has sides, diminished by four right angles, (or, which is the same thing, to twice as many right angles as the...

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

Euclid - Euclid's Elements - 1833 - 183 pages
...formed as many triangles as the figure has sides, and therefore all their angles taken together are equal to twice as many right angles as the figure has sides (1): but the angles at the point F are equal to four right angles (2); and therefore the angles of...

## Inductive Geometry, Or, An Analysis of the Relations of Form and Magnitude ...

Charles Bonnycastle - Geometry - 1834 - 631 pages
...expressed as the following proposition : "The interior angles of any closed plane figure are together equal to twice as many right angles as the figure has sides, minus four right angles." 206. And as a second application of the principle in question, or, which...

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

Mathematics - 1835
...has as many angles as sides : therefore all the interior angles together with four right angles are equal to twice as many right angles as the figure has sides. Therefore, &c. Cor. The four angles of a quadrilateral are together equal to four right angles. SECTION...

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

Euclid - 1835 - 513 pages
...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, by...

## 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 equal to four...

## The Element of Geometry

John Playfair - Geometry - 1836 - 114 pages
...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. COR. II. All the exterior angles of any rectilineal figure are together equal to four right angles....

## A Treatise on Mensuration for the Use of Schools

Commissioners of National Education in Ireland - Measurement - 1837 - 262 pages
...as you go along, as also the angles. angles, A, B, C, &c. of the figure together, and their sum must be equal to twice as many right angles as the figure has sides, wanting four right angles. But when the figure has a re-enterant angle, as F, measure the external angle, which...