## 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

Now , this Propofition is a Theorem , not a Definition ; because the equality of

Figures of any kind must be

though this were a true Propofition , it ought to have been

indeed ...

Now , this Propofition is a Theorem , not a Definition ; because the equality of

Figures of any kind must be

**demonstrated**, and not affumed ; and , therefore ,though this were a true Propofition , it ought to have been

**demonstrated**. Butindeed ...

Page 17

Which was to be

at the base of an Isosceles triangle are equal to one another ; and , if the equal

sides be produced , the angles upon the other side of the base Thall be equal .

Which was to be

**demonstrated**. a 10. Axi PRO P. V. THE O R. THE THE anglesat the base of an Isosceles triangle are equal to one another ; and , if the equal

sides be produced , the angles upon the other side of the base Thall be equal .

Page 18

... since it has been

whole ACF , the parts of which , the angles CBG , BCF , are allo equal ; the

remaining angle ABC is therefore equal to the remaining angle ACB , which are

the angles ...

... since it has been

**demonstrated**, that the whole angle ABG is equal to thewhole ACF , the parts of which , the angles CBG , BCF , are allo equal ; the

remaining angle ABC is therefore equal to the remaining angle ACB , which are

the angles ...

Page 24

... ABC ; but the angles CBE , EBD have been

same three angles ; and things that are equal to the same are equal to one

another ; therefore the angles CBE , EBD are equal to the angles DBA , ABC ; but

CBE ...

... ABC ; but the angles CBE , EBD have been

**demonstrated**to be equal to thesame three angles ; and things that are equal to the same are equal to one

another ; therefore the angles CBE , EBD are equal to the angles DBA , ABC ; but

CBE ...

Page 25

Ar . angle ABD , the less to the greater , which is impossible ; therefore BE is not

in the fame straight line with BC . And , in like manner , it may be

that no other can be in the same straight line with it but BD , which therefore is in

...

Ar . angle ABD , the less to the greater , which is impossible ; therefore BE is not

in the fame straight line with BC . And , in like manner , it may be

**demonstrated**,that no other can be in the same straight line with it but BD , which therefore is in

...

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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.