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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.
Euclid's Elements [book 1-6] with corrections, by J.R. Young - Page 41
by Euclides - 1838

## The first two books of the Elements of Euclid, with additional figures ...

Euclides - 1852 - 152 pages
...that is a , together with four right angles. . 2 Cor Therefore all the angles of the figure, XT - *• together with four right angles, are equal to twice as many right angles as the figure has sides. [The triangle furnishes an instance of this, for all its angles are together equal to two right angles;...

## The English Journal of Education, Volume 6

Education - 1852 - 512 pages
...EUCLID. SECTION I. — 1. The angles at the base of an isosceles triangle are equal to each other. 2. All the interior angles of any rectilineal figure,...together with four right angles, are equal to twice us many right angles as the figure has sides. 3. To a given straight line to apply a parallelogram...

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

Charles Davies - Geometry - 1886 - 334 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 sides. But the sum of all the angles about the point P is equal to four right angles (Th. ii. Cor. 4) ; and...

## Elements of Geometry and Trigonometry

Adrien Marie Legendre - Geometry - 1852 - 436 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...

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

Royal Military Academy, Woolwich - Mathematics - 1853 - 400 pages
...angles CBA, BAC, ACB, are equal to two right angles. Wherefore, if a side of a triangle, etc. QED COR. 1. All the interior angles of any rectilineal figure,...with four right angles, are equal to twice as many D right angles as the figure has sides. E.«=^lT"\~~-^, \ 4C-\ For any rectilineal figure ABCDE can...

## The synoptical Euclid; being the first four books of Euclid's Elements of ...

Euclides - 1853 - 146 pages
...triangles; that is, (I. 15. Cor. 2.) together with four right angles. Therefore all the angles of the figure, together with four right angles, are equal...twice as many right angles as the figure has sides. COK. 2. — All the exterior angles of any rectilineal figure are together equal to four right angles....

## The first six books of the Elements of Euclid, with numerous exercises

Euclides - 1853 - 176 pages
...triangles : that is (i. 15, cor. 2), together with four right angles. Therefore all the angles of the figure, together with four right angles, are equal...twice as many right angles as the figure has sides. Сод. 2. All the exterior angles of any rectilineal figure are together equal to four right ,ingles....

## The Elements of Euclid: With Many Additional Propositions ..., Part 1

Euclid - Geometry - 1853 - 176 pages
...internal angles, are equal to twice as many right angles as the figure has sides; but the internal angles, together with four right angles, are equal to twice as many right angles as the figure has sides (6); take away from both the internal angles, and the external angles remain, equal to four right angles...