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

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Page 13

**Parallel**straight lines , are such as are in the fame plane , and which , being produced ever so far both ways , do not meet . ual Gdes . t angle . POSTULAT E S. obtufc ang L . 1 . ET it be granted that a straight line may be drawn from ... Page 34

IF a straight line falling upon two other straight lines makes the alternate angles equal to one another , these two straight lines shall be

IF a straight line falling upon two other straight lines makes the alternate angles equal to one another , these two straight lines shall be

**parallel**. Let the straight line EF , which falls upon the two straight lines AB , CD , make ... Page 35

I. AB is

I. AB is

**parallel**to CD . Again , because the angles BGH , GHD 5 27.1 . are equal to two right angles , and that AGH , BGH are allo < By Hyp . equal d to two right angles ; the angles AGH , BGH are equal d 13. Page 36

29. le Traight lines which are

29. le Traight lines which are

**parallel**to the same straight line are**parallel**to one another . Let AB , CD be each of them**parallel**to EF ; AB is also**parallel**to CD . Let the straight line GHK cut AB , EF , CD ; and because GHK cuts ... Page 37

E AF is drawn through the given point A

E AF is drawn through the given point A

**parallel**to the given Book I. straight line BC . Which was to be done . PROP . XX.XII . THEOR . IF a side of any triangle be produced , the exterior angle is equal to the two interior and opposite ...### What people are saying - Write a review

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### Common terms and phrases

added alſo altitude angle ABC angle BAC baſe becauſe Book caſe centre circle circle ABCD circumference common cone cylinder definition demonſtrated deſcribed diameter divided double draw drawn equal equal angles equiangular equimultiples exceſs fame fides figure firſt folid fore four fourth given angle given in poſition given in ſpecies given magnitude given ratio given ſtraight line greater Greek half join leſs likewiſe magnitude manner meet muſt oppoſite parallel parallelogram perpendicular plane priſm produced prop proportionals propoſition pyramid reaſon rectangle rectangle contained rectilineal remaining right angles ſame ſecond ſegment ſhall ſides ſimilar ſolid ſphere ſquare ſquare of AC Take taken theſe third triangle ABC wherefore whole

### Popular passages

Page 483 - The circumference of every circle is supposed to be divided into 360 equal parts, called degrees ; and each degree into 60 equal parts, called minutes ; and each minute into 60 equal parts, called seconds ; and these into thirds, &c.

Page 170 - 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 81 - THE straight line drawn at right angles to the diameter of a circle, from the extremity of...

Page 105 - DEF are likewise equal (13. i.) to two right angles ; therefore the angles AKB, AMB are equal to the angles DEG, DEF, of which AKB is equal to DEG ; wherefore the remaining angle AMB is equal to the remaining angle DEF.

Page 167 - AC the same multiple of AD, that AB is of the part which is to be cut off from it : join BC, and draw DE parallel to it : then AE is the part required to be cut off.

Page 10 - When a straight line standing on another straight line makes the adjacent angles equal to one another, each of the angles is called a right angle; and the straight line which stands on the other is called a perpendicular to it.

Page 62 - AB be the given straight line ; it is required to divide it into two parts, so that the rectangle contained by the whole, and one of the parts, shall be equal to the square of the other part.

Page 112 - To describe an equilateral and equiangular pentagon about a given circle. • Let ABCDE be the given circle; it is required to describe an equilateral and equiangular pentagon about the circle ABCDE. Let the angles of a pentagon, inscribed in the circle...

Page 200 - If two triangles have two angles of the one equal to two angles of the other, each to each, and one side equal to one side, viz. either the sides adjacent to the equal...

Page 38 - F, which is the common vertex of the triangles ; that is, together with four right angles. Therefore all the angles of the figure, together with four right angles, are equal to twice as many right angles as the figure has sides.