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Hence, the interior angles plus four right angles, is equal to twice as many right angles as the polygon has sides, and consequently, equal to the sum of the interior angles plus the exterior angles.
Elementary Geometry: With Applications in Mensuration - Page 34
by Charles Davies - 1850 - 216 pages

## Plane Geometry Suggestive Method

George Clinton Shutts - 1905 - 260 pages
...angles. Let AD represent any convex polygon. To prove that the sum of the interior angles of the polygon is equal to twice as many right angles as the polygon has sides, minus four right angles. Suggestion 1. Connect each vertex with O, any point within the polygon. 2....

## Annual Report of the Commissioners ..., Volume 70

1905 - 946 pages
...parallel to the base and half of it. D Papen. 6. The sum of all the interior angles of any polygon and four right angles is equal to twice as many right angles as there are eides to the polygon. 7. Find a point which shall be equally distant from the three angles...

## Examination Questions for Certificates of Competency as Mine Inspector, Mine ...

Mining engineering - 1907 - 578 pages
...are there in the remaining angle? M — ///. ANS. — The sum of the interior angles of any polygon is equal to twice as many right angles as the polygon has sides, less four right angles. In this case, the figure having four sides, the sum of all the interior angles...

## Intermediate Geometry: Being Sections V and VI of "geometry, Theoretical and ...

Walter Percy Workman - Geometry - 1908 - 228 pages
...exterior angles so formed are together equal to four right angles ; and in any convex polygon the sum of the interior angles, together with four right angles, is equal to twice as many right angles as the figure has sides (Euc. I. 32, Cor.) 110 Congruence. CI — If two triangles have two sides and the...

## Special Reports on Educational Subjects, Volume 24

Great Britain. Board of Education - Education - 1911 - 678 pages
...angle." In the same way it was shown on the board that the sum of the interior angles of a convex polygon is equal to twice as many right angles as the polygon has sides less two. This theorem was to be repeated at the next lesson ; and the boys were asked to prove as...

## A Treatise on Surveying, Part 1

Surveying - 1911 - 338 pages
...close jK,lygon, which may be summarised as follows. The sum of the ' interior' angles augmented by four right angles is equal to twice as many right angles as i 'he figure has sides. The sum of the ' exterior ' angles diminished by four right angles is equal...

## The Coal Miner's Handbook: A Handy Reference Book for Coal Miners, Pit ...

International Correspondence Schools - Coal mines and mining - 1913 - 360 pages
...of the exterior angles will equal four right angles. 18. The sum of the interior angles of a polygon is equal to twice as many right angles as the polygon has sides, less four right angles. For example, the sum of the interior angles of a quadrilateral is (2X4)—...

## The Elements of Surveying and Geodesy

William Charles Popplewell - Geodesy - 1915 - 272 pages
...the number of sides. Stated precisely, " the sum of all the internal angles of a closed polygon plus four right angles is equal to twice as many right angles as the figure has sides." So that it is easy from the field notes to find the internal angle at each corner...