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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.
Elements of Geometry and Conic Sections - Page 32
by Elias Loomis - 1857 - 226 pages

## Mathematics: Compiled from the Best Authors and Intended to be the ..., Volume 2

Mathematics - 1801
...;• add all the inward angles A, B, C, &c. together, and when the work is right, their sum will be equal to twice as many right angles, as the figure has sides, wanting four right angles. And when there is an angle, as F, that bends inward, and you measure the external angle, which is less...

## The Elements of Euclid: Also the Book of Euclid's Data ...cor. viz. The ...

Robert Simson - Trigonometry - 1804
...Q^ED . 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 fides. For any reCtilineal figure ABCDE can be divided into as many triangles as the figure has fides,...

## The Elements of Euclid: The Errors, by which Theon, Or Others, Have Long Ago ...

Robert Simson - Trigonometry - 1806 - 518 pages
...gether 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. 2. All the exterior angles of any rectilineal figure, are together equal to four right angles....

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

John Playfair - Euclid's Elements - 1806 - 311 pages
...as many right angles as the figure has sides, wanting four. For all the angles exterior and interior are equal to twice as many right angles as the figure has sides, and the exterior are equal to four right angles ; therefore the interior are equal to twice as many...

## A Course of Mathematics in Two Volumes for the Use of Academies as Well as ...

Charles Hutton - Mathematics - 1807
...work ; add all the inward angles A, B, c, &c, together ; for when the work is right, their sum will ba equal to twice as many right angles as the figure has sides, wanting 4 right angles. But when there is an angle, as F, that bends inwards, and you measure the external...

## Elements of Geometry, Geometrical Analysis, and Plane Trigonometry ...

Sir John Leslie - Geometry, Analytic - 1809 - 524 pages
...AED, is equal to two right angles. All the exterior angles therefore, added to the interior angles, are equal to twice as many right angles as the figure has sides. Consequently the exterior angles are equal to the four right angles which, by the last Proposition,...

## Elements of Geometry, Geometrical Analysis, and Plane Trigonometry: With an ...

Sir John Leslie - Geometry, Plane - 1809 - 493 pages
...is equal to two right angles. All the exterior angles therefore, added to the interior angles, ftre equal to twice as many right angles as the figure has sides. Consequently the exterior angles are equal to the four right angles which, by the last Proposition,...

## A Course of Mathematics ...: Composed for the Use of the Royal Military ...

Charles Hutton - Mathematics - 1811
...triangles, is equal to two right angles (th. 17); therefore the sum of the angles of all the triangles is equal to twice as many right angles as the figure has sides. But the sum of all the angles about the point P, which are so many many of the angles of the triangles,...