Books Books Thus when it is said that the sum of the three angles of any triangle is equal to two right angles, this is a theorem, the truth of which is demonstrated by Geometry. Elements of Mechanical Drawing - Page 22
by Gardner Chace Anthony - 1894 - 98 pages ## A Course of Mathematics: For the Use of Academies as Well as ..., Volume 1

Charles Hutton - Mathematics - 1812
...which some property is asserted, and the truth of it required to be proved. Thus, when it is said that, The sum of the three angles of any triangle is equal to two right angles, this is a Theorem, the truth of which is demonstrated by Geometry. — A set or collection of such... ## A Course of Mathematics: For the Use of Academies, as Well as Private ...

Charles Hutton - Mathematics - 1822 - 618 pages
...some property is asserted, and the truth of it required to be .proved. Thus, when it is said that, The sum of the three angles of any triangle is equal to two right angles, this is a Theorem, the truth of which is demonstrated by Geometry. — A set or collection of such... ## Prize Essay and Lectures, Delivered Before the American Institute ..., Volume 5

American Institute of Instruction - Education - 1835 - 318 pages
...work, this author has pursued a different method in regard to parallel lines, by first proving that the sum of the three angles of any triangle is equal to two right angles ; but the demonstration is tedious and difficult for beginners, and is therefore rarely understood.... ## An Elementary Treatise on Plane and Solid Geometry

Benjamin Peirce - Geometry - 1837 - 216 pages
...perpendicular to its base, divides it, by art. 57, into the two equal triangles ABC and ABG. 64. Theorem. The sum of the three angles of any triangle is equal to two right angles. Demonstration. Let ABC (fig. 36) be the given triangle. Produce AC to D, and draw CE parallel to AB.... ## A Treatise on Algebra

Elias Loomis - Algebra - 1846 - 380 pages
...statement of some property, the truth of which is required to be proved. Thus when it is said that the sum of the three angles of any triangle is equal to two right angles, this is a theorem, the truth of which is demonstrated by Geometry. (8.) A problem is a question requiring... ## A Treatise on Algebra

Elias Loomis - Algebra - 1846 - 346 pages
...statement of some property, the truth of which is required to be proved. Thus when it is said that the sum of the three angles of any triangle is equal to two right angles, this is a theorem, the truth of which is demonstrated by Geometry. (8.) A. problem is a question requiring... ## An Elementary Treatise on Plane and Solid Geometry

Benjamin Peirce - Geometry - 1847 - 150 pages
...perpendicular to its base, divides it, by § 57, into the two equal triangles ABC and ABG. 65. Theorem. The sum of the three angles of any triangle is equal to two right angles. Proof. Let ABC (fig. 36) be the given triangle. Produce AC to D, and draw CE parallel to AB. The angles... ## A Treatise on Algebra

Elias Loomis - Algebra - 1855 - 352 pages
...the statement of some property, the truth of which is required to be proved. Thus the principle that the sum of the three angles of any triangle is equal to two right angles, is a theorem, the truth of which is demonstrated by Geometry. (8.) A problem is a question requiring... ## Elements of Geometry, and Plane and Spherical Trigonometry: With Numerous ...

Horatio Nelson Robinson - Geometry - 1860 - 472 pages
...the theorem ; the sum of the angles of any parallelogram it eoual tc four right angles. THEOREM XI. The sum of the three angles of any triangle is equal to two right angles. Let AB C be a triangle, and through its vertex C / draw a line parallel to the b\e/a base AB, and produce... 