## The Elements of Euclid, Viz: The Errors, by which Theon, Or Others, Have Long Ago Vitiated These Books, are Corrected; and Some of Euclid's Demonstrations are Restored. Also the Book of Euclid's Data, in Like Manner Corrected. the first six books, together with the eleventh and twelfth |

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Page 6

Equal “ and Gmilar

of the fame Number and Magnitude . ” Now , this Propofition is a Theorem , not a

Definition ; because the equality of Figures of any kind must be demonstrated ...

Equal “ and Gmilar

**folid**Figures are those which are contained by “ fimilar Planesof the fame Number and Magnitude . ” Now , this Propofition is a Theorem , not a

Definition ; because the equality of Figures of any kind must be demonstrated ...

Page 198

A cube is a solid figure contained by fix equal squares , XXVI . A tetrahedron is a

solid figure contained by four equal and equilateral triangles . XXVII . An

octahedron is a

XXVIII .

A cube is a solid figure contained by fix equal squares , XXVI . A tetrahedron is a

solid figure contained by four equal and equilateral triangles . XXVII . An

octahedron is a

**folid**figure contained by eight equal and equilateral triangles .XXVIII .

Page 213

... the angles DAB , DAC ; therefore BAC , with either of them , is greater than the

other . Wherefore , if a solid angle , & c . Q. E. D. b 4. 1 . C 20. I. PRO P. XXI . THE

O R. E'which together are lefs than four right angles . First , Let the

... the angles DAB , DAC ; therefore BAC , with either of them , is greater than the

other . Wherefore , if a solid angle , & c . Q. E. D. b 4. 1 . C 20. I. PRO P. XXI . THE

O R. E'which together are lefs than four right angles . First , Let the

**folid**angle at ... Page 214

Take in each of the straight lines AB , AC , AD any points m B , C , D , and join BC

, CD , DB : Then , because the

angles CBA , ABD , a 20 , II . DBC , any two of them are greater than the third ;

there ...

Take in each of the straight lines AB , AC , AD any points m B , C , D , and join BC

, CD , DB : Then , because the

**folid**angle at B is contained by the three plainangles CBA , ABD , a 20 , II . DBC , any two of them are greater than the third ;

there ...

Page 215

... greater than all the angles of the polygon , as has been proved . Wherefore the

remaining angles of the triangles , viz . those at the vertex , which contain the

solid angle at A , are less than four right angles . Therefore every

.

... greater than all the angles of the polygon , as has been proved . Wherefore the

remaining angles of the triangles , viz . those at the vertex , which contain the

solid angle at A , are less than four right angles . Therefore every

**folid**angle , & c.

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### Common terms and phrases

added alſo altitude angle ABC angle BAC baſe becauſe Book Book XI caſe circle circle ABCD circumference common cone cylinder definition demonſtrated deſcribed diameter divided double draw drawn equal equal angles equiangular equimultiples exceſs fame fides firſt folid fore four fourth given angle given in poſition given magnitude given ratio given ſtraight line greater Greek half join leſs likewiſe magnitude manner meet muſt oppoſite parallel parallelogram perpendicular plane produced prop proportionals propoſition pyramid radius rectangle rectangle contained 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 32 - 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 165 - D ; wherefore the remaining angle at C is equal to the remaining angle at F ; Therefore the triangle ABC is equiangular to the triangle DEF.

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 10 - When several angles are at one point B, any ' one of them is expressed by three letters, of which ' the letter that is at the vertex of the angle, that is, at ' the point in which the straight lines that contain the ' angle meet one another, is put between the other two ' letters, and one of these two is...

Page 55 - 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 of the line between the points of section, is equal to the square of half the line.

Page 32 - ... then shall the other sides be equal, each to each; and also the third angle of the one to the third angle of the other. Let ABC, DEF be two triangles which have the angles ABC, BCA equal to the angles DEF, EFD, viz.

Page 45 - To describe a parallelogram that shall be equal to a given triangle, and have one of its angles equal to a given rectilineal angle.

Page 211 - AB shall be at right angles to the plane CK. Let any plane DE pass through AB, and let CE be the common section of the planes DE, CK ; take any point F in CE, from which draw FG in the plane DE at right D angles to CE ; and because AB is , perpendicular to the plane CK, therefore it is also perpendicular to every straight line in that plane meeting it (3.

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.

Page 304 - Thus, if B be the extremity of the line AB, or the common extremity of the two lines AB, KB, this extremity is called a point, and has no length : For if it have any, this length must either be part of the length of the line AB, or of the line KB.