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ECF; and they are adjacent angles. But, when the adjacent angles which one straight line makes with another straight line are equal to one another, each of them is called a right IT angle ; therefore each of the angles DCF, ECF, is a right angle.
Stories about Mathematics-land - Page 69
by D. Ponton - 1927

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

Robert Simson - Trigonometry - 1806 - 546 pages
...; therefore the angle DCF e&1. is equal c to the angle ECF; and they are adjacent angles. But, when the adjacent angles which one straight line makes with another straight line are equal to one another, each of them •110. Def. is called a right d angle ; therefore each of the...

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

Euclides - 1816 - 588 pages
...• 3. 1. -fore the angle DCF is%eequal0 to the angle ECF ; and they ,are adjacent angles. But, when the adjacent angles which one straight line makes with another straight line are 10 Def. equal to one anotlfci, ra1 h of them is called a right d angle; therefore each of the angles...

## Elements of Geometry: Containing the First Six Books of Euclid: With a ...

John Playfair - 1819 - 354 pages
...therefore the angle DCF is equal (8. 1.) to the angle ECF ; and they are adjacent angles. But, when the adjacent angles which one straight line makes with another straight line are equal to one another, each of them is called a right (7. def.) angle ; therefore each of the angles...

## Euclid's Elements of Geometry: The Six First Books. To which are Added ...

Rev. John Allen - Astronomy - 1822 - 508 pages
...(Def. 20). PROP. XIII. THEOR. The angles (ABC, ABD), which me right line (AB), makes with another (CD), on one side of it, are together equal to two right angles. FyA. Cor.—If more right lines stand on the same right line (CD), on the same side of it, and at the...

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

Robert Simson - Trigonometry - 1827 - 546 pages
...base EF ; therefore the angle DCF is equal* to the angle ECF; and they are adjacent angles. But when the adjacent angles which one straight line makes with another straight line, are equal to one another, each of them is called a right* angle; therefore each of the angles DCF,...

## Elements of Geometry: Being Chiefly a Selection from Playfair's Geometry

John Playfair - Geometry - 1829 - 210 pages
...straight line AB. ; PROPOSITION XIII. THEOREM. The two angles which one straight line makes with another, on one side of it, are together equal to two right angles* Let the straight line AB make with CD, on one side of CD, the angles ABC, ABD; these are together equal...

## Geometry Without Axioms; Or the First Book of Euclid's Elements. With ...

Thomas Perronet Thompson - Euclid's Elements - 1833 - 168 pages
...the third side EF ; therefore the angle DCF is* equal to ECF ; and they are adjacent angles. But when the adjacent angles which one straight line makes with another straight line are fI.Nom.37. equal to one another, each of them ist a right angle ; therefore each of the angles...

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

Euclid - 1835 - 540 pages
...therefore the angle DCF is equal c to the c g. j angle ECF; and they are adjacent angles. But when the adjacent angles which one straight line makes with another straight line are equal to one another, each of them is called a right d angle ; therefore each of the angles DCF,...

## The First Six and the Eleventh and Twelfth Books of Euclid's Elements: With ...

Euclid, James Thomson - Geometry - 1837 - 410 pages
...therefore, the angle DCF is equal ( I. 8.) to the angle ECF ; and they are adjacent angles. But, when the adjacent angles which one straight line makes with another straight line, are equal to one another, each of them is called (I. def. 8.) a right angle; therefore each of the...

## Elements of Geometry: Containing the First Six Books of Euclid : with a ...

John Playfair - Euclid's Elements - 1837 - 332 pages
...therefore the angle DCF is equal (8. 1.) to the angle EOF ; and they are adjacent angles. But, when the adjacent angles which one straight line makes with another straight line are equal to one another, each of them is called a right (7. def.) angle ; therefore each jf the angles...