Books Books
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

## Plane and Solid Geometry

Isaac Newton Failor - Geometry - 1906 - 431 pages
...Scalene. f Isosceles. fc Oblique. Acute. Scalene. f Isosceles. . Obtuse. PROPOSITION XL THEOREM 153 The sum of the three angles of a triangle is equal to two right angles.* HYPOTHESIS. ABC is any triangle. CONCLUSION. PROOF Draw MN through B II to AC, and produce...

## Exercises in Concrete Geometry: With Supplementary Discussions

David Sands Wright - Geometry - 1906 - 104 pages
...the bisectors of a pair of supplementary adjacent angles meet at an angle of 90°. 5. Theorem. The sum of the three angles of a triangle is equal to two right angles. 1. How many degrees in each angle of the triangle ABC, if they are in the proportion of 1,...

## Introduction and books 1,2

Euclid - Mathematics, Greek - 1908 - 550 pages
...to the bearing of these propositions upon Euclid's Postulate 5 ; and the next theorem is VII. If the sum of the three angles of a triangle is equal to two right angles, through any point in a plane there can only be drawn one parallel to a given straight line....

## A Study of Mathematical Education Including the Teaching of Arithmetic

Benchara Branford - Arithmetic - 1908 - 434 pages
...body of scientific theorems. Allman attributes to Thales the discovery of the two theorems — (a) The sum of the three angles of a triangle is equal to two right angles ; (&) The sides of equi-angular triangles are proportional. (Hence the basis of the theory of...

## The Journal of Philosophy, Psychology and Scientific Methods, Volume 6

Electronic journals - 1909 - 756 pages
...eloquently, and we can not stifle her voice. But our intellect also tells us, and with equal force, that the sum of the three angles of a triangle is equal to two right angles, and we are unable to rebel against its authority. If we see God behind the categorical imperative,...

## The Dublin University Calendar, Volume 1

Trinity College (Dublin, Ireland) - 1909 - 546 pages
...the length of the perpendicular from an extremity of its base on the opposite side. 3. Prove that the sum of the three angles of a triangle is equal to two right angles. 4- If a straight line is divided into two parts, prove that the sum of the squares at the whole...

## The Collected Mathematical Papers of James Joseph Sylvester ...

James Joseph Sylvester - Mathematics - 1909 - 712 pages
...the degree to which (x - a) rises in the denominator of fx. t Take as an example the theorem that the sum of the three angles of a triangle is equal to two right-angles : as soon as by a stroke of the imagination a line is conceived as drawn from one angle...

## Wentworth's Plane Geometry

George Albert Wentworth, David Eugene Smith - Geometry, Plane - 1910 - 287 pages
...side of the transversal are supplementary, the lines are parallel. PROPOSITION XIX. THEOREM 107. The sum of the three angles of a triangle is equal to two right angles. c Given the triangle ABC. Y To prove that Z .4 + Z 7?+ Z (7 = 2 rt. A. Proof. Suppose BY drawn...