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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.
Elementary Geometry: With Applications in Mensuration - Page 33
by Charles Davies - 1850 - 216 pages

## The Young Gentleman's Arithmetick, and Geometry: Containing Such Elements of ...

Edward Wells - Arithmetic - 1723 - 358 pages
...the Sum of all the Angles in all the Tri~ angles, into which the Figure is divided, will together be equal to twice as ma-ny right Angles, as the Figure has Sides. But the Angles about P, the inward Point of each Figure, wherein all the Triangles concur, are (by Corol. 4....

## A Royal Road to Geometry: Or, an Easy and Familiar Introduction to the ...

Thomas Malton - 1774 - 484 pages
...the Sides. ie equal to four Right Angles. And, all the internal Angles of any Right-lined Figure are equal to twice as many Right Angles as the Figure has Sides, wanting four, (Th. i. i0. i.) confequently, the external Angles being equal to thofe four (Th. 2. of...

## A Complete Treatise on Practical Mathematics: Including the Nature and Use ...

John McGregor (teacher of mathematics.) - Mathematics - 1792 - 532 pages
...been accurately taken, adá all the inward angles into one fum ; and when the work is right, their fum is equal to twice as many right angles as the figure has fides, wanting 4 right angles, (Euclid 31.1. Cor. 1.) Or, inftead of the inward angles, their füpplements...

## Mathematics: Compiled from the Best Authors and Intended to be the ..., Volume 2

Mathematics - 1801 - 658 pages
...;• add all the inward angles A, B, C, &c. together, and when the work is right, their sum will be equal to twice as many right angles, as the figure has sides, wanting four right angles. And when there is an angle, as F, that bends inward, and you measure the...

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

John Playfair - Mathematics - 1806 - 320 pages
...if a side of a triangle, &c. QED "7^ COR. 1. All the interior angles of any rectilineal figure are equal to twice as many right angles as the figure has sides, wanting four right angles. For any rectilineal figure ABCDE can be divided into as many triangles as...

## The Elements of Euclid: The Errors, by which Theon, Or Others, Have Long Ago ...

Robert Simson - Trigonometry - 1806 - 546 pages
...D, 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...

## A Course of Mathematics in Two Volumes for the Use of Academies as Well as ...

Charles Hutton - Mathematics - 1807 - 464 pages
...work ; add all the inward angles A, B, c, &c, together ; for when the work is right, their sum will ba equal to twice as many right angles as the figure has sides, wanting 4 right angles. But when there is an angle, as F, that bends inwards, and you measure the external...

## Elements of Geometry, Geometrical Analysis, and Plane Trigonometry: With an ...

Sir John Leslie - Geometry, Plane - 1809 - 522 pages
...is equal to two right angles. All the exterior angles therefore, added to the interior angles, ftre equal to twice as many right angles as the figure has sides. Consequently the exterior angles are equal to the four right angles which, by the last Proposition,...