## Euclid's Elements [book 1-6] with corrections, by J.R. Young1838 |

### From inside the book

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**parallel**lines and proportion have led geometers ; and have entered at length upon several topics of interest to the critical reader , I have thought it better to refer at once to that treatise , for this kind of miscella- neous ... Page 9

... these , are called Trape- ziums . XXXI .

... these , are called Trape- ziums . XXXI .

**Parallel**straight lines are such as are in the same plane , and which , being produced ever so far both ways , do not meet . POSTULATES . I. LET it be granted , that a BOOK I. DEFINITIONS . Page 34

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**parallel**. Let the straight line EF , which falls upon the two straight lines AB , CD , make the alternate angles AEF , EFD equal to one another : AB shall be**parallel**to CD . For , if it be not**parallel**, AB and CD being produced will ... Page 35

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**parallel**to CD . Because the angle EGB is + Hyp . equal to the angle GHD , * 15 . 1. and the angle EGB equal to the angle AGH , therefore the angle +1 . Ax . # 27 . 1 . * Hyp . # 13 . 1 . tl Ax . 13 Ax . +27 . 1 : A- C K -B -D AGH is ... Page 36

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**parallels**some have attributed to the definition of**parallels**- from the negative property of their never meeting : yet as this property fully and sufficiently characterises this class of lines , we are inclined to trace the perplexity ...### Other editions - View all

### Common terms and phrases

ABCD adjacent angles alternate angles angle ABC angle ACB angle BAC angle BCD angle EDF angles equal antecedent arc BC base BC BC is equal bisected centre circle ABC circumference consequent Const demonstrated described diameter double draw equal angles equal to AC equiangular equilateral and equiangular equimultiples Euclid exterior angle fore Geometry given circle given straight line gnomon greater inscribed join less Let ABC Let the straight logarithm multiple opposite angle parallel parallelogram pentagon perpendicular PROB proportion proposition Q. E. D. PROP radius rectangle contained rectilineal figure remaining angle segment side BC similar sine square of AC straight line AB straight line AC tangent THEOR touches the circle triangle ABC triangle DEF twice the rectangle wherefore

### Popular passages

Page 30 - IF two triangles have two sides of the one equal to two sides of the other, each to each, but the angle contained by the two sides of one of them greater than the angle contained by the two sides equal to them, of the other ; the base of that which has the greater angle shall be greater than the base of the other.

Page 105 - The angle in a semicircle is a right angle; the angle in a segment greater than a semicircle is less than a right angle; and the angle in a segment less than a semicircle is greater than a right angle.

Page 50 - To a given straight line to apply a parallelogram, which shall be equal to a given triangle, and have one of its angles equal to a given rectilineal angle.

Page 61 - If a straight line be divided into two equal parts, and also into two unequal parts ; the rectangle contained by the unequal parts, together with the square on the line between the points of section, is equal to the square on half the line.

Page 65 - If a straight line be divided into any two parts, four times the rectangle contained by the whole line and one of the parts, together with the square of the other part, is equal to the square of the straight line which is made up of the whole and that part.

Page 70 - To divide a given straight line into two parts, so that the rectangle contained by the whole, and one of the parts, may be equal to the square of the other part.

Page 41 - All the interior angles of any rectilineal figure, together with four right angles, are equal to twice as many right angles as the figure has sides.

Page 172 - If two triangles have one angle of the one equal to one angle of the other and the sides about these equal angles proportional, the triangles are similar.

Page 45 - TRIANGLES upon the same base, and between the same parallels, are equal to one another.

Page 38 - If a, straight line fall upon two parallel straight lines, it makes the alternate angles equal to one another; and the exterior angle equal to the interior and opposite upon the same side; and likewise the two interior angles upon the same side together equal to two right angles.