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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 Royal Road to Geometry: Or, an Easy and Familiar Introduction to the ... - Page 213
by Thomas Malton - 1774 - 440 pages

## Elements of Geometry: With Notes

John Radford Young - Euclid's Elements - 1827 - 246 pages
...in each triangle amounts to two right angles, therefore the angles of all the triangles are together equal to twice as many right angles as the figure has sides, that is to say, the sum of the angles of the polygon, together with those about the point within it,...

## Elements of the Geometry of Planes and Solids: With Four Plates

Ferdinand Rudolph Hassler - Electronic book - 1828 - 180 pages
...angles, as AGD, GDE, and so on, standing in equal segments, are equal to one another; and their sum being equal to twice as many right angles as the figure has sides wanting four: that is, eight right angles, each of these angles of the hexagon is equal eight sixths of one right...

## The First Six Books of the Elements of Euclid, with a Commentary and ...

Euclid, Dionysius Lardner - Euclid's Elements - 1828 - 544 pages
...COR. 10. — All the internal angles of any rectilinear figure ABCDE, together with four right angles, are equal to twice as many right angles as the figure has sides. Take any point F within the figure, and draw the right, lines FA, FB, FC, FD, and F E. There are formed...

## A London Encyclopaedia, Or Universal Dictionary of Science, Art ..., Volume 10

Thomas Curtis - Aeronautics - 1829 - 814 pages
...figure В С DE ; and the interior angles of that figure, together with four right angles, being also equal to twice as many right angles as the figure has sides (Theorem XX.), the angles of the triangles are equal to the interior angles of the plane figure and...

## Elements of Geometry: Being Chiefly a Selection from Playfair's Geometry

John Playfair - Geometry - 1829 - 186 pages
...xr = (n— 2) x 2r, that is, all the interior angles of any convex rectilineal figure are together equal to twice as many right angles as the figure has sides less two sides. " Es. PROPOSITION M. THEOREM. All the exterior angles of any convex rectilineal figure,...

## Geometry, Plane, Solid, and Spherical, in Six Books: To which is Added, in ...

Pierce Morton - Geometry - 1830 - 584 pages
...is equal to two right angles (2.) ; all the interior angles, together with all the exterior angles, are equal to twice as many right angles as the figure has angles. But all the exterior angles are, by the former part of the proposition, equal to four right...

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

John Playfair - Euclid's Elements - 1832 - 333 pages
...angles as the figure has sides; but the exterior are equal to four right angles; therefore the interior are equal to twice as many right angles . as the figure has sides, wanting four. PROP. II. Two straight lines, which make with a third line the interior ancles on the same side of...

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

Thomas Perronet Thompson - Euclid's Elements - 1833 - 150 pages
...ABD, isf equal to two right angles ; all the interior together with all the exterior angles of the figure, are equal to twice as many right angles as the figure has sides. But (by Cor. 1 .) all the interior angles are together equal to twice as many right angles as the figure'...