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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: Containing the First Six Books of Euclid: With a ... - Page 308
by John Playfair - 1819 - 317 pages

## The Elements of Euclid: Viz. the First Six Books, Together with the Eleventh ...

Euclides - 1816 - 592 pages
...&c. QED COR. 1. 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. For any rectilineal figure ABCDE, can be divided into as many triangles as the figure has sides, by...

## Euclid's Elements of Geometry: The Six First Books. To which are Added ...

Rev. John Allen - Astronomy - 1822 - 518 pages
...two right angles [13. 1} ; therefore all the exterior and interior angles of the figure are together equal to twice as many right angles as the figure has sides ; but the interior angles are equal to twice as many right angles, except four, as the figure has sides [by the...

## Euclid's Elements of Geometry: The Six First Books. To which are Added ...

Rev. John Allen - Astronomy - 1822 - 508 pages
...as many right angles, except four, as the figure has sides ; and all tbe angles of these triangles are equal to twice as many right angles as the figure has sides (32. 1 /CM.), therefore the angles of these triangles which are at their common vertex A, being those...

## The First Six Books with Notes

Euclid - 1822 - 216 pages
...are formed as many triangles as the figure has sides, and, therefore, all their angles taken together are equal to twice as many right angles as the figure has sides ( 1 ), but the angles at the point F are equal to four right <z) Cor. 3. angles, (2), and therefore...

## A Course of Mathematics: For the Use of Academies, as Well as Private ...

Charles Hutton - Mathematics - 1822 - 616 pages
...; add all the inward angles A, n, c, &.c. together ; for when the work is right, their sum will be equal to twice as many right angles as the figure has sides, wanting 4 right angles. But when there is an angle, a* r, (hat bends inward*, and yon measure the external...

## A treatise on navigation, and nautical astronomy

Edward Riddle - Nautical astronomy - 1824 - 572 pages
...twice as many right angles as the figure has sides ; or the interior angles of the figure, themselves, are equal to twice as many right angles as the figure has sides, wanting four right angles. QED Cor. 1. All the interior angles of any quadrilateral figure are together...

## A Popular Course of Pure and Mixed Mathematics ...: With Tables of ...

Peter Nicholson - Mathematics - 1825 - 1058 pages
...QE I). Cor. 1 . All the interior angles of any rectilínea] figure, together with four right angles, are equal to twice as many right angles as the figure has sides. For any rectilineal figure ABCDE can be divided into as many triangles as the figure has sides, by...

## Elements of Arithmetic, Algebra, and Geometry

George Lees - 1826 - 276 pages
...to all the angles of the figure, together with four right angles ; that is, the angles of the figure are equal to twice as many right angles, as the figure has sides wanting four. PROP. XIII. THEOREM. If two triangles, BAG, EOF, have two angles, BAG, ABC, and a side...