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

### From inside the book

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Page 17

3 AB to DE , and AC to DF ; and the

3 AB to DE , and AC to DF ; and the

**angle BAC**equal to the angle EDF , the base BC fhall be equal to the bafe EF and the triangle ABC to the triangle DEF ; and the other angles , to which the equal fides are oppofite , fhall be equal ... Page 20

F But , if one of the vertices , as D , be within the other trig angle ACB ; produce AC , AD to E , F ; therefore , becaufe AC is equal to AD in the triangle ACD , the angles ECD ... The

F But , if one of the vertices , as D , be within the other trig angle ACB ; produce AC , AD to E , F ; therefore , becaufe AC is equal to AD in the triangle ACD , the angles ECD ... The

**angle BAC**is e- qual to the angle EDF . Page 21

I. cides with the base EF , the fides BA , AC cannot but coincide with the fides ED , DF ; wherefore likewife the

I. cides with the base EF , the fides BA , AC cannot but coincide with the fides ED , DF ; wherefore likewife the

**angle BAC**coincides with the angle EDF , and is equal to it . There . b . s . Ax • fore if two triangles , & c . Page 26

Let ABC be a triangle , and let its fide BC be produced to D , the exterior

Let ABC be a triangle , and let its fide BC be produced to D , the exterior

**angle**ACD is greater than either of the interior oppofite**angles**CBA ,**BAC**. Bifecta AC in E , join BE and produce it to F , and make EF equal to BE ; join also ... Page 27

thefe add the

thefe add the

**angle**ACB ; therefore the**angles**ACD , ACB are Book I. greater than the**angles**ABC , ACB ; but ACD , ACB are ... In like manner , it may be demonftrated , that**BAC**, ACB , as also CAB , ABC are less than two right**angles**.### What people are saying - Write a review

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### Common terms and phrases

added alfo alſo altitude angle ABC angle BAC bafe baſe becauſe bifected Book Book XI centre circle circle ABCD circumference common cone cylinder defcribed definition demonftrated diameter divided double draw drawn equal equal angles equiangular equimultiples excefs fame fame multiple fecond fegment fhall fides fimilar firft folid folid angle fore four fourth fquare fquare of AC ftraight line given angle given in fpecies given in pofition given magnitude given ratio greater Greek half join lefs magnitude meet oppofite parallel parallelogram perpendicular plane prifms produced PROP propofition proportionals pyramid rectangle rectangle contained remaining right angles Take taken thefe THEOR theſe third triangle ABC wherefore whole

### Popular passages

Page 474 - 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.