Books Books 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 Plane Geometry - Page 46
by Thomas Hunter - 1878 - 132 pages ## Euclid's Elements [book 1-6] with corrections, by J.R. Young

Euclides - 1838 - 264 pages
...with four right angles. Therefore all the angles of the figure, together with four right angles, are equal to twice as many right angles as the figure has sides. COB. 2. — All the exterior angles of any rectilineal figure are together equal to four right angles.... ## A Treatise on Geometry and Its Application in the Arts

Dionysius Lardner - Curves, Plane - 1840 - 386 pages
...external angles ; for, the sum of all the angles internal and external including the convex angles, is equal to twice as many right angles as the figure has sides, together with the excess of every convex angle above two right angles. But the sum of the internal... ## Euclid's Elements of plane geometry [book 1-6] with explanatory appendix ...

Euclides - 1840 - 194 pages
...right angles. Therefore, all the external, with all the internal angles of the figure, are together equal to twice as many right angles as the figure has sides ; that is to say, according to the preceding corollary, they are equal to all the internal angles of... ## Elements of Geometry

Adrien Marie Legendre - Geometry - 1841 - 288 pages
...C ; for, by adding to each the angle ABC, the sums are each equal to two right angles. THEOREM. 64. The sum of all the interior angles of a polygon is equal to as many times two right angles as there are units in the number of sides minus two. Fig. 42. Demonstration.... ## The Elements of Euclid; viz. the first six books,together with the eleventh ...

Euclides - Geometry - 1841 - 378 pages
...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... ## Arithmetical Spyglass and Teacher's Assistant: Intended as a Key and ...

Charles Waterhouse - Arithmetic - 1842 - 180 pages
...sum of the three angles is equal to two right angles ; in a square, there are four right angles, 5. The sum of all the interior angles of a polygon, is equal to as many times two right angles as there are units in the number of sides less two. NOTE. — A re-entering... ## Elements of Geometry: Containing the First Six Books of Euclid, with a ...

John Playfair - Euclid's Elements - 1842 - 332 pages
...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. COR. 2. All the exterior angles of any rectilineal figure are together equal to four... ## Elements of geometry: consisting of the first four,and the sixth, books of ...

Euclides - 1842 - 320 pages
...with four right angles. Therefore all the angles of the figure, together with four right angles, are equal to twice as many right angles as the figure has sides. COR. 2. All the exterior angles of any rectilineal figure are together equal to four right angles.... ## Elementary and practical Arithmetic on the inductive system, by analysis and ...

Charles WATERHOUSE - Arithmetic - 1844 - 228 pages
...two right angles. -3. In an isosceles triangle, the angles opposite to the equal sides are equal. 4. The sum of all the interior angles of a polygon, is equal to as many two right angles, as there are units in the number of sides, less two. 5. Of two sides of a... 