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
| Science - 1857
...first book of the ' Elements.' The proposition required by Euclid is the thirty-second, viz. that the **sum of the three angles of a triangle is equal to two right** angles ; given that proposition, the difficulty about parallels disappears, inasmuch as their properties... | |
| Elias Loomis - Conic sections - 1857 - 226 pages
...the sum of its angles diminished by two right angles, and multiplied by theNuiadrantal 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... | |
| Elias Loomis - Conic sections - 1858 - 234 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... | |
| Josiah Lyman - Protractors - 1862 - 77 pages
...also the arc BD is the supplement of the arc AB ; and BCD is the supplement of the angle ACB. 11. The **sum of the three angles of a triangle is equal to two right** angles, or 180°. Hence, if the sum of any two angles of a triangle be subtracted from 180°, the remainder... | |
| Thomas Hill - Geometry - 1863 - 136 pages
...thr gles about the point A, and their sum is plainly two ! angles. 37. The mode of proving that the **sum of the three angles of a triangle is equal to two right** angles, by cutting a piece of card, is called experimental proof. It is of very little use in mathematics,... | |
| C. Davies - Mathematics - 1867 - 324 pages
...second, by Prob- VIII ; then will the angle HEF be equal to the third angle of the triangleFor, the **sum of the three angles of a triangle is equal to two right** angles (Bk- I- Th- xvii) ; and the sum of the three angles on the same side of the line DE fe equal... | |
| Geometry - 1868
...it make the angles FGH=A, and HGK=B, then KGE will equal the third angle of the triangle, since the **sum of the three angles of a triangle is equal to two right** angles. At C and D make angles equal to HGK and KGE, and let their sides meet in O; then OCD is the... | |
| Nashville (Tenn.). Board of Education - Public schools - 1869
...great.y developed. For example, the child can be led to discover, by means of his protractor, that the **sum of the three angles of a triangle, is equal to two** right-angles, or that the vertical angles formed by the intersection of two lines, are equal. When... | |
| Bowdoin College, George Lincoln Goodale - Science - 1870
...easy to gather every day, would be to deny a truth which in its way is as plainly shown as that the **sum of the three angles of a triangle is equal to two right** angles. If now it is announced to us that for the production of another kind of dropsy there is needed... | |
| |