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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

## A System of Practical Mathematics: ... With a Plain Account of the Gregorian ...

John Potter - Mathematics - 1753 - 568 pages
...of the Sides is oppofite the given Angle ; but mud be folved by the fecond Rule, Page 224. Now, as the three Angles of every Triangle are equal to two right Angles, or 180°, the Angle at A 36° . 40', being fubtrafted from 180°, leaves 143° . 20', the Sum of the...

## The Elements of Euclid: The Errors, by which Theon, Or Others, Have Long Ago ...

Robert Simson - Trigonometry - 1762 - 488 pages
...oppofite angles of any quadrilateral figure defcribed in a circle, are together equal to two right T angles. Let ABCD be a quadrilateral figure in the circle ABCD ; any two of its oppofite angles are together equal to two right angles. Join AC, BD ; and becaufe the three angles...

## Euclid's Elements of Geometry: The First Six, the Eleventh and Twelfth Books

Euclid - Geometry - 1765 - 492 pages
...it : I fay, its oppofite angles are equal to two right angles. Join Ac, BD. Then becaufe [by 32. i.] the three angles of every triangle are equal to two right angles, the three angles CAB, ABc, BC A of the triangle ABC will be equal to two right angles. But [by 2I. 3.] the angle c AB...

## A Royal Road to Geometry: Or, an Easy and Familiar Introduction to the ...

Thomas Malton - 1774 - 482 pages
...wanting four ; and by the 2nd, all the external Angles are equal to four Right Angles. Alfo, by the loth, the three Angles of every Triangle are equal to two Right Angles; and all the Angles, about a Point, are equal to four; (2.i.) confequently, fince the three Angles DEF,...

## The Elements of Euclid, Viz: The Errors, by which Theon, Or Others, Have ...

Robert Simson - Trigonometry - 1775 - 534 pages
...PROP. XXII. THEO R. THE oppofite angles of any quadrilateral figure deleribed in a circle, are together equal to two right angles. Let ABCD be a quadrilateral figure in the circle ABCD ; any two of its oppofite angles are together equal to two right angles. Join AC, BD ; and becaufe the three angles...

## The Elements of Euclid,: In which the Propositions are Demonstrated in a New ...

Euclid - Geometry - 1776 - 318 pages
...angles0;, therefore the fix angles ABD, ABC, ACB, v ACD, ADC, ADB, are greater than two right angles: But c the three angles of every triangle are equal to two right angles • therefore the nine angles CBA, BCA, BAC, ACD, CAD, ADC, ADB, ABD, DAB, ate equal to fix right angles...

## The First Six Books: Together with the Eleventh and Twelfth

Euclid - 1781 - 550 pages
...PROP. XXII. THEO R. THE oppofite angles of any quadrilateral figure defcribed in a circle, are together equal to two right angles. Let ABCD be a quadrilateral figure in the circle ABCD ; any two of its oppofite angles are together equal to two right angles. Join AC, BD ; and becaufe the three angles...

## The Elements of Euclid: The Errors, by which Theon, Or Others, Have Long Ago ...

Robert Simson - Trigonometry - 1781 - 534 pages
...XXTI. THEO R- . THE oppofite angles of any quadrilateral figure deferibed in a circle, are together equal to two right angles. Let ABCD be a quadrilateral figure in the circle ABCD i arry two of its oppofite angle* are together equal to two right angles. Join AC, BD ; and becaufe...