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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.
New Elementary Geometry: With Practical Applications ; a Shorter Course Upon ... - Page 29
by Benjamin Greenleaf - 1873 - 176 pages

## The geometry, by T. S. Davies. Conic sections, by Stephen Fenwick

...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 and Trigonometry from the Works of A.M. Legendre ...

Charles Davies - Geometry - 1854 - 436 pages
...are 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 angles multiplied by...

## A Manual for Practical Surveyors

E. W. Beans - Surveying - 1854 - 114 pages
...taken. If the entire survey has been made as above directed, the sum of all the internal angles will be equal to twice as many right angles as the figure has sides, diminished by four right angles. If this sum, as in practice will be likely to be the case, should...

## The popular educator, Volumes 5-6; Volume 8

Popular educator - 1854
...into three equal parts. *"'t 3Fig. .42. No. 3. interior angles together with four right angles are equal to twice as many right angles as the figure has sides. Therefore all the interior angles together with all the exterior angles are equal (Ax. 1) to all the...

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

William Mitchell Gillespie - Surveying - 1855 - 436 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. " Calculate...

## Elements of Geometry and Trigonometry: With Applications in Mensuration

Charles Davies - Geometry - 1855 - 336 pages
...triangles is equal to two right angles (Th- xvii) : hence, the sum of the angles of all the triangles is equal to twice as many right angles as the figure has sidesBut the sum of all the angles about the point P is equal to four right angles (Th- ii- Cor- 4)...

## The Elements of geometry; or, The first six books, with the eleventh and ...

Euclides - 1855
...and there are as many triangles in the figure as it has sides, all the angles of these triangles are equal to twice as many right angles as the figure has sides. But all the angles of these triangles are equal to the interior angles of the figure, viz. ABС, BСD,...

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

William Mitchell Gillespie - Surveying - 1856 - 478 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. " Calculate...