## The Elements of Euclid: The Errors, by which Theon, Or Others, Have Long Ago Vitiated These Books, are Corrected and Some of Euclid's Demonstrations are Restored. Also, to this Second Edition is Added the Book of Euclid's Data. In Like Manner Corrected. viz. the first six books, together with the eleventh and twelfth |

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Now this Proposition is a Theorem , not a Definition , because the equality of figures of any kind

Now this Proposition is a Theorem , not a Definition , because the equality of figures of any kind

**must**be demonstrated , ' and not aisumed . and therefore , tho ' this were a true Propofition , it ought to have been demonstrated . Page 19

For if it be not greater , AC A

For if it be not greater , AC A

**must**either be equal to AB , or less than it . it is not equal , because then the angle ABC would be equal to the angle ACB ; but it ' Book 1. than the angle ACB ; but it. Page 21

O to three given straight lines ; but any two whatever of these

O to three given straight lines ; but any two whatever of these

**must**be greater than the thirda . Let A , B , C be the three given straight lines , of which any two whatever are greater than the third , viz . Page 24

Book I. For if it be not greater , it

Book I. For if it be not greater , it

**must**either be equal to it , or less . mbut the angle BAC is not equal to the angle EDF , because then the base BC would be equal to EF . but it A D is not ; therefore the anglc BAC is not equal to ... Page 27

A G For if AGH be not equal to GHD , B one of them

A G For if AGH be not equal to GHD , B one of them

**must**be greater than the other ; let AGH be the greater . and be- C. H D cause the angle AGH is greater than th๋ F angle GHD , add to each of them the angle BGH ; therefore the angles ...### What people are saying - Write a review

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### Common terms and phrases

added alſo altitude angle ABC angle BAC baſe BC is given becauſe Book caſe circle circle ABCD circumference common cone contained 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 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 remaining right angles ſame ſecond ſegment ſhall ſhewn ſides ſimilar ſolid ſquare ſquare of BC taken THEOR theſe third thro triangle ABC wherefore whole

### Popular passages

Page 5 - Let it be granted that a straight line may be drawn from any one point to any other point.

Page 163 - 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 48 - If a straight line be divided into any two parts, the squares of the whole line, and of one of the parts, are equal to twice the rectangle contained by the whole and that part, together with the square of the other part. Let the straight line AB be divided into any two parts in the point C; the squares of AB, BC are equal to twice the rectangle AB, BC, together with the square of AC.

Page 73 - The straight line drawn at right angles to the diameter of a circle, from the extremity of it, falls without the circle; and no straight line can be drawn from the extremity between that straight line and the circumference, so as not to cut the circle...

Page 105 - 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 3 - A circle is a plane figure contained by one line, which is called the circumference, and is such that all straight lines drawn from a certain point within the figure to the circumference, are equal to one another.

Page 167 - Similar triangles are to one another in the duplicate ratio of their homologous sides.

Page 54 - 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 47 - 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 37 - To describe a parallelogram that shall be equal to a given triangle, and have one of its angles equal to a given rectilineal angle.