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The opposite angles of any quadrilateral figure described in a circle, are toe/ether equal to two right angles. Let ABCD be a quadrilateral figure in the circle ABCD : any two of its opposite angles are together equal to two right angles.
Euclid in Paragraphs: The Elements of Euclid: Containing the First Six Books ... - Page 71
by Euclid - 1845 - 199 pages

The Wesleyan methodist association magazine, Volume 16

1853 - 618 pages
...would be no moral discipline in believing religious truths, any more than there is in believing that the three angles of every triangle are equal to two right angles, or any other proposition in Euclid. And in making our spiritual life one of faith, God has acted in...

Annual Report and Documents, Volumes 35-42

New York (State) School for the deaf, White Plains - 1854 - 936 pages
...triangle be produced, the exterior angle will be equal to the two interior and opposite angles ; and the three angles of every triangle are equal to two right angles." DBC Let ABC be a triangle, in which the side BC is produced towards D, then will the exterior angle...

Elements of geometry and mensuration

Thomas Lund - Geometry - 1854 - 522 pages
...join OE; and let OE, or OE c produced meet the circumference in F. Then AOE is a triangle; and since the three angles of every triangle are equal to two right angles, and one of them in this case, viz. t OAE is a right angle, .'. each of the other two angles, tOEA,...

The Artillerists̓ Manual, and British Soldiers̓ Compendium

Frederick Augustus Griffiths - Artillery drill and tactics - 1854 - 406 pages
...radii, its sides become the sines of the opposite angles, or the cosines of the adjacent angles. 5. The three angles of every triangle are equal to two right angles ; hence the oblique angles of a right-angled triangle are each other-s complements. 6. The sum of the...

The Elements of geometry; or, The first six books, with the eleventh and ...

Euclides - 1855 - 262 pages
...are together equal to two right angles. Let AB СD be a quadrilateral figure in the circle AB СD. Any two of its opposite angles are together equal to two right angles. Join A С and B D. The angle СAB is equal to the angle СDB (III. 21), because they are in the same segment...

The geometry of the three first books of Euclid, by direct proof from ...

Euclides - 1856 - 168 pages
...quadrilateral figure inscribed in a circle are together equal to two right angles. Let A BCD (Fig. 50) be a quadrilateral figure in the circle ABCD, any...angles are together equal to two right angles. Join AC, DB ; and take the angles ADB, BDC, into which any of the angles AD C is divided by the line D B. Then...

Fundamental Philosophy, Volume 2

Jaime Luciano Balmes - Philosophy - 1856 - 568 pages
...say, to a little more or less, but never be perfect exactness. Consequently we could not assert that the three angles of every triangle are equal to two right angles ; all that we could say would be, that so far as our experience goes, we have observed that in all...

Baptism in Its Mode and Subjects

Rev. Alexander Carson - Baptism - 1857 - 572 pages
...not a head for the philosophy of language : and I say this with as little bad feeling as I say that the three angles of every triangle are equal to two right angles. PASSAGES OF SCRIPTURE QUOTED OR REFERRED TO Chap. Ver. Page GENESIS, i. 26 .... 147 lii. 1 218 Chap....