 | Peter Nicholson - 1856 - 518 sider
...; but the sum of the two angles BAC, BAD, is equal to two right angles (theorem 1) ; therefore the sum of the three angles of a triangle is equal to two right angles. 80. COROLLARY 1. — If two angles of one triangle be equal to two angles of another triangle,... | |
 | 1857 - 1142 sider
...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... | |
 | Josiah Lyman - 1862 - 92 sider
...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 - 1863 - 164 sider
...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,... | |
 | New York (N.Y.). Board of Education. Superintendent of Schools - 1867 - 132 sider
...the necessaries of life, or of filling the pocket, it may be difficult to determine. That the s\im of the three angles of a triangle is equal to two right angles, and that the Greeks drove back the Persian invaders, are facts which per se might appear to... | |
 | James Maurice Wilson - 1868 - 132 sider
...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... | |
 | 1869 - 794 sider
...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... | |
 | Charles Davies - 1870 - 392 sider
...second, by Prob. VIII ; then will the angle HEF be equal to the third angle of the triangle. For, the sum of the three angles of a triangle is equal to...of the three angles on the same side of the line DE is equal to two right angles (Bk. I. Th. ii. Cor. 2) ; hence. if DEC and CEH are equal to two of the... | |
 | Trinity College (Hartford, Conn.) - 1870 - 1008 sider
...side of a triangle is less than the sum and greater than the difference of the other two sides. 2. The sum of the three angles of a triangle is equal to two right angles. 3. The diagonals of a parallelogram bisect each other. 4. An inscribed angle is measured by... | |
 | Bowdoin College - 1870 - 428 sider
...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... | |
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After remarking that the mathematician positively knows that the sum of the three angles of a triangle is equal to two right angles... 
