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" ... the three angles of a triangle are together equal to two right angles, although it is not known to all. "
The Works of John Playfair ...: With a Memoir of the Author ... - Page 335
by John Playfair - 1822
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Antiquities of the Orient Unveiled: Containing a Concise Description of the ...

Moses Wolcott Redding, Author of Guide to Mount Moriah - 1875 - 570 pages
...Geometry, Astronomy, and Mathematics. It is to him that the world is indebted for the discovery that the three angles of a triangle are together equal to two right angles, and that in any right angled triangle, the square formed on the hypothenuse is equal to the sum of...
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Preparing to Teach: For Study by Sabbath-school Teachers and Training Classes

John Hall - 1875 - 428 pages
...an opinion as we please ; if we reject a fact, we only advertise our stupidity. If a man denies that the three angles of a triangle are together equal to two right angles, we can demonstrate the proposition. If he says that Brutus did not kill Csesar, we can open the books...
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The Luminous Unity: Or, Letters Addressed to the Rev. A. Guinzburg, a Rabbi ...

Matthew R. Miller - 1876 - 276 pages
...probably a horrible Inquisition would have flourished for a century, founded on the question whether the three angles of a triangle are together equal to two right angles. I have had some knowledge by personal experience of the unfairness of Universalists in their arguments...
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Modern geometry [ed.] with an appendix by W.B. Jack

Richard Wormell - 1876 - 268 pages
...XVIII. The exterior angle of any triangle is equal to the two interior and opposite angles together, and the three angles of a triangle are together equal to two right angles. Let А В С be a triangle of which А С D is the exterior angle ; then shall and Л С А В + ЛABC+...
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Primer of geometry

Francis Cuthbertson (geometer.) - 1876 - 102 pages
...is = the two angles BAC, ABC together. Wherefore if one side of a triangle &c. QED PROPOSITION XX. The three angles of a triangle are together equal to two right angles. Let ABC be a A. Then shall its three angles be together equal to two right angles. Produce BCtoD. Then...
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Practical Plane Geometry, Volume 30

E. S. Burchett - 1876 - 188 pages
...study of Euclid should observe the following points, that may be culled from the First Book : — 1st. The three angles of a triangle are, together, equal to two right angles, invariably. 2nd. The triangle has the same number of equal sides that it has equal angles. 3rd. The...
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The Princeton review. May-Dec. 1878

1878 - 958 pages
...and as we do so we discover that they have certain properties involved in their very nature, and that the three angles of a triangle are together equal to two right angles, and that parallel lines cannot meet. The properties of the ellipse, as demonstrated by Apollonius,...
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Mathews' Euclid examination papers ... on Euc. i.-iv

Edward Harri Mathews - 1879 - 94 pages
...necessarily true as it stands ? Having completed the enunciation, prove the proposition. 3. Prove that the three angles of a triangle are together equal to two right angles ; and investigate the sum of the exterior angles of any plane convex polygon. 4. Show how to bisect...
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The Moral Philosophy of Aristotle: Consisting of a Translation of the ...

Aristotle, Walter Mooney Hatch - 1879 - 658 pages
...demonstrated as necessary ; if, for example, any one ' opines ' after a process of demonstration that ' the angles of a triangle are together equal to two right angles,' the opinion which he has is a neee*#ary truth. Other opinions are drawn from the senses, and hence some...
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The pupil teachers' handy mathematical and grammatical question-book, with key

Pupil teachers - 1880 - 1486 pages
...Proof.@Because the triangle ABD is equilateral, therefore the triangle ABD is equiangular (i. 5, Cor.) the three angles of a triangle are together equal to two right angles (i. 32), therefore the angle ABD is equal to a third of two right angles, that is, two-thirds of a...
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