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Books Books 21 - 30 of 180 on After remarking that the mathematician positively knows that the sum of the three....  
" 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 218
by Euclid, Sir Thomas Little Heath, Johan Ludvig Heiberg - 1908
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Philosophical Magazine

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...
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Elements of geometry and conic sections

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...
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Elements of Geometry and Conic Sections

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...
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A Manual of the Protracting Trigonometer: With Its Application to ...

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...
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A Second Book in Geometry

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,...
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Elements of Geometry and Trigonometry

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...
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Annual Report

New York (N.Y.). Board of Education. Superintendent of Schools - Education - 1867
...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...
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Elementary Geometry, Volume 1

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...
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Annual Report of the Public Schools ...

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...
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Bowdoin Scientific Review: A ..., Volume 1, Issue 1 - Volume 2, Issue 28

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...
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