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If a side of any triangle be produced, the exterior angle is equal to the two interior and opposite angles ; and the three interior angles of every triangle are equal to two right angles.
The First Six, and the Eleventh and Twelfth Books of Euclid's Elements: With ... - Page 27
by Euclid, James Thomson - 1845 - 352 pages

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

Robert Simson - Trigonometry - 1762 - 488 pages
...to the two interior and oppofite angles ; and the three interior angles of every triangle are ec(ual to two right angles. Let ABC be a triangle, and let one of its fides BC be produced to D. the exterior angle ACD is equal to the two interior and oppofite angles...

## The Popular Educator, Volumes 1-2; Volume 12

Geography - 1867 - 964 pages
...в together make up the angle r> с в, which is therefore equal to the angles с в А, в A c. 7. The three interior angles of every triangle are together equal to two right anglet. In Fig. 5 the angle BCD has been shown to be equal to the angles с в А, в А с ; to each...

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

Robert Simson - Trigonometry - 1775 - 534 pages
...equal to the two interior and oppofite angles ; and the three interior angles of every triangle are equal to two right angles. Let ABC be a triangle, and let one of its fides BC be produced to D ; the exterior angle ACD is equal to the two interior and oppofite angles...

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

Euclid - 1781 - 552 pages
...equal to the two interior and oppofite angles ; and the three interior angles of every triangle are equal to two right angles. Let ABC be a triangle, and let one of its fides BC be produced to D ; the exterior angle ACD is equal to the two interior and oppofite angles...

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

Robert Simson - Trigonometry - 1781 - 534 pages
...equal to the two interior and oppofite angles ; and the three interior angles of every triangle are equal to two right angles. Let ABC be a triangle, and let one of its fides BC be produced to D. the exterior angle ACD is equal to the two interior and oppofite angles...

## The History of Philosophy, from the Earliest Times to the ..., Volume 1

William Enfield, Johann Jakob Brucker - Early works to 1800 - 1791 - 610 pages
...four. Of the geometrical theorems afcribed to Pythagoras, the following are the principal; that the interior angles of every triangle are together equal to two right angles; that the only polygons which will fill up the whole fpace about a given point, are the equilateral...

## Elements of Geometry;: Containing the First Six Books of Euclid, with Two ...

Euclid, John Playfair - Euclid's Elements - 1795 - 462 pages
...equal to the two interior and oppofite angles ; and the three interior angles of every triangle are equal to two right angles. Let ABC be a triangle, and let one of its fides BC be produced to D ; the exterior angle ACD is equal to the two in- . terior and oppofite angles...

## The Elements of Euclid: Viz. the First Six Books, with the Eleventh and ...

Alexander Ingram - Trigonometry - 1799 - 374 pages
...equal to the two interior and oppoiite angles ; and the three interior angles of every triangle are equal to two right angles. Let ABC be a triangle, and let one of its fides BC be produced to D ; the exterior angle ACD is equal to the two interior and oppofite angles...