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
| WILLIAM T HARRIS - 1884
...negation ; and, of course, what is true of triangle is true of all general ideas ; they are negations. The **sum of the three angles of a triangle is equal to two right** angles. This is a proposition to be demonstrated. I draw a triangle, and prove that the three angles... | |
| Euclid - Euclid's Elements - 1885 - 312 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... | |
| Antonio Rosmini-Serbati - 1885
...mathematical affirmations — for example, "The consequence is contained in the principle," or " The **sum 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... | |
| Euclid - Euclid's Elements - 1885 - 312 pages
...B. LEGENDRE'S AND HAMILTON'S PROOFS or EUCLID, i. xxxn. The discovery of the Proposition that "the **sum of the three angles of a triangle is equal to two right** angles ' ' is attributed to Pythagoras. Until modern times no proof of it, independent of the theory... | |
| Education - 1888
...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... | |
| Antonio Rosmini - Psychology - 1886
...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... | |
| Joseph Baldwin - Educational psychology - 1887 - 299 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,... | |
| Education - 1887
...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... | |
| Gabriel Compayré - Education - 1887 - 491 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... | |
| George Albert Wentworth - Geometry - 1888 - 386 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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