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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... "
Yale University Entrance Examinations in Mathematics: 1884 to 1898 - Page 125
1898 - 208 pages
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The first six books of the Elements of Euclid, and propositions i.-xxi. of ...

Euclides - 1885 - 340 pages
...two angles ABC, CDA equal to the sum of the three angles ACD, DAC, CDA of the triangle ACD ; but the sum of the three angles of a triangle is equal to two right angles [I. xxxn.]. Therefore the sum of ABC, CDA is two right angles. Or thus : Let O be the centre...
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The Academy: A Journal of Secondary Education, Volume 2

Education - 1888 - 634 pages
...etc., €tc., and that we shall one day die. On this hypothesis all general knowledge, such as " the sum of the three angles of a triangle is equal to two right angles," is impossible, for this statement transcends the experience of any individual. The second...
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Psychology, Volume 2

Antonio Rosmini - Psychology - 1886 - 660 pages
...mathematical affirmations — for example, "The consequence is contained in the principle," or " The sura of the three angles of a triangle is equal to two right angles " — then the copulative is signifies only ideal being. If the affirmation descends to the...
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Lectures on Pedagogy: Theoretical and Practical

Gabriel Compayré - Education - 1887 - 516 pages
...mentioned above ; but it should be recollected that no "System of mere measurements can ever prove that the sum of the three angles of a triangle is equal to two right angles. (P.) 421. ARE THERE OBJECT-LESSONS IN ARITHMETIC AND GEOMETRY ? — We do not think that there...
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Proceedings of the Board of Public Instruction of the City of Albany, Volume 11

Education - 1887 - 720 pages
...What is an isoscles triangle '( an equilateral triangle ; a scalene triangle f 22-24 Prove that the sum of the three angles of a triangle is equal to two right angles. 26-27. Name three ways in which triangles may be proved equal. 28-30. Prove that in a triangle...
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Elementary Psychology and Education: A Text-book for High Schools, Normal ...

Joseph Baldwin - Educational psychology - 1887 - 332 pages
...Mental Phenomena. — I perceive the beautiful lily, I remember the cheering song. I discern that the sum of the three angles of a triangle is equal to two right angles. I grieve over the loved and lost. I determine to study psychology. I perceive myself remembering,...
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A Text-book of Geometry

George Albert Wentworth - Geometry - 1888 - 264 pages
...third side, and their difference is less than the third side. PROPOSITION XXIII. THEOREM. -/ 138. The sum of the three angles of a triangle is equal to two right angles. A Let ABC be a triangle. To prove Z B + Z BCA + ZA = 2 rt. A. Proof. Suppose CE drawn II to...
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Manual of Christian Evidences

George Park Fisher - Apologetics - 1888 - 166 pages
...never have seen London, but we have not a whit more doubt that London exists than we have that the sum of the three angles of a triangle is equal to two right angles. We never saw Napoleon the First, but we are not less certain that Napoleon lived than we are...
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Greek Geometry from Thales to Euclid

George Johnston Allman - Geometry - 1889 - 266 pages
...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 (d), refers to the discovery of the property of a circle that all triangles described...
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Manual of Plane Geometry: On the Heuristic Plan, with Numerous Extra ...

George Irving Hopkins - 1891 - 210 pages
...side of a triangle is less than the sum of the other two, and greater than their difference. 98. The sum of the three angles of a triangle is equal to two right angles. Sug. Consult Theorems 58 and 87. 99. If one side of a triangle be extended, the exterior angle...
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