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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 66
by Charles Hutton - 1811

## A Treatise on Land-surveying: Comprising the Theory Developed from Five ...

William Mitchell Gillespie - Surveying - 1857 - 524 pages
...proposition of Geometry, that in any figure bounded by straight lines, the sum of all the interior angles is equal to twice as many right angles, as the figure has sides less two ; since the figure can be divided into that number of triangles. Hence this common rule. "...

## Elements of Geometry and Trigonometry: From the Works of A.M. Legendre

Adrien Marie Legendre - Geometry - 1857 - 448 pages
...triangles in the figure ; that is, as many times as there are sides, less two. But this product is equal to twice as many right angles as the figure has sides, less four right angles. Cor. 1. The sum of the interior angles in a quadrilateral is equal to two right...

## Elements of Geometry and Conic Sections

Elias Loomis - Conic sections - 1858 - 234 pages
...that is, together with four right angles (Prop. V., Cor. 2). Therefore the angles of the polygon are equal to twice as many right angles as the figure has sides, wanting four right angles. Cor. 1. The sum of the angles of a quadrilateral is four right angles ; of a pentagon,...

## The Practice of Engineering Field Work, Applied to Land, Hydrographic, and ...

W. Davis Haskoll - Civil engineering - 1858 - 324 pages
...and in an irregular polygon they may be all unequal. The interior angles of a polygon are together equal to twice as many right angles as the figure has sides, less four. On this is based the theory of the traverse, of which further explanation will be given...

## Euclid's Elements of plane geometry [book 1-6] explicitly enunciated, by J ...

Euclides - 1860
...a polygon be produced to meet, the sum of the salient angles thus formed, with eight right angles, will be equal to twice as many right angles as the figure has sides. Let ABCDE be a polygon, and let its sides produced meet in F, G, H, T, K ; then the sum of the salient...

## Elements of Geometry, and Plane and Spherical Trigonometry: With Numerous ...

Horatio Nelson Robinson - Geometry - 1860 - 453 pages
...triangles is equal to two right angles, (Th. 11) ; and the sum of the angles of all the triangles must be equal to twice as many right angles as the figure has sides. But the sum of these angles contains the sum of four right angles about the point p ; taking these...

## The examination papers as set for the preliminary literary examination of ...

...two right angles ; and all the angles of any rectilineal figure, together with four right angles, are equal to twice as many right angles as the figure has sides. 6. The opposite sides and angles of parallelograms are equal to one another, and the diameter bisects...

## Euclid's Elements of plane geometry [book 1-6] explicitly enunciated, by J ...

Euclides - 1860
...of a polygon be produced to meet, the sum of the salient angles thus formed with eight right angles, will be equal to twice as many right angles as the figure lias sides. 16. If on two opposite sides of a rectangle semicircles be described lying on corresponding...