After remarking that the mathematician positively knows that the sum of the three angles of a triangle is equal to two right angles... Introduction and books 1,2 - Page 218by Euclid, Sir Thomas Little Heath, Johan Ludvig Heiberg - 1908Full view - About this book
| Elias Loomis - Geometry - 1871 - 58 pages
...the sum of its angles diminished by two right angles, and multiplied by the quadrantal triangle. Cor. **If the sum of the three angles of a triangle is equal to** three right angles, its surface will be equal to the quadrantal triangle ; if the sum is equal to four... | |
| Henry Barnard - Education - 1872
...catch either into other cogged wheels, or into pinions, or into trundles, Ac. Of the Triangk. — The **sum of the three angles of a triangle is equal to two** right-angles, Ac. Of similar Triangles. — Two triangles are similar when the angles of one are equal... | |
| Henry Barnard - Education - 1872
...catch either into other cogged wheels, or into pinions, or into trundles, Ac. Of the Triangle. — The **sum of the three angles of a triangle is equal to two** right-angles, Ac. Of eimiiar Triangle*. — Two triangles are similar when the ingles of one ar» equal... | |
| 1873
...side in -each respectively equal ; (c) when they have three sides in each respectively equal. 6. The **sum of the three angles of a triangle is equal to two right** angles. I7. The sum of the interior angles of a polygon is equal to twice as many right angles as the... | |
| Education - 1874
...heartfelt pleasure and profound satisfaction from the contemplation of that wonderful truth, that the **sum of the three angles of a triangle is equal to two right** angles. My friend, who sits before me, used to take particular delight in putting this at me, when... | |
| Education - 1874
...heartfelt pleasure and profound satisfaction from the contemplation of that wonderful truth, that the **sum of the three angles of a triangle is equal to two right** angles. My friend, who sits before me, used to take particular delight in putting this at me, when... | |
| Thomas F. Harrison, Norman Allison Calkins - Teaching - 1875 - 269 pages
...equality as a definite fact, and inequality indefinitely. Thus, it is required to be proved that the **sum of the three angles of a triangle is equal to two right** angles ; also, that, of any two sides of a triangle, that which lies opposite to the greater angle... | |
| Aaron Schuyler - Geometry - 1876 - 372 pages
...equal. 76. Exercises. 1. Prove by means of the annexed diagram, in which DE is parallel to AC, that the **sum of the three angles of a triangle is equal to two right** angles. 2. The sum of the three straight lines drawn from any point within a triangle to the vertices... | |
| Humanities - 1877
...drawn from the preceding notices. First inference. — Thales must have known the theorem that the **sum of the three angles of a triangle is equal to two right** angles. Pamphila, in [<f], refers to the discovery of the property of a circle that all triangles described... | |
| George Albert Wentworth - Geometry - 1877 - 402 pages
...a point to a straight line make equal acute angles with that line. PROPOSITION XXL THEOREM. 98. The **sum of the three angles of a triangle is equal to two right** angles. BE C Let ABC be a triangle. We are to prove ZB + ZB CA + ZA = two rt. A Draw CE II to AB, and... | |
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