## The First Six Books with Notes |

### From inside the book

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Page 2

The

The

**angle**(**ABC**) which is greater than a right**angle**, is called obtuse . 13. The**angle**( ABD ) which is less than a right**angle**, is całed acute . 14. A plane figure is a plane surface , which is bounded on all sides by one or more ... Page 6

A In an isosceles triangle ( B.1C ) the

A In an isosceles triangle ( B.1C ) the

**angles**at the base (**ABC**and ACB ) are equal to one another ; and if the equal sides be produced , the**angles**below the base ( FBC and GCB ) shall also be equal . B Take any point F in the side ... Page 8

See N. If two triangles , (

See N. If two triangles , (

**ABC**and EFD ) have two sides of the one respectiv ly equal to two sides of the other , ( AB to EF'and BC to FD ) , and also have the base ( AC ) equal to the base ( ED ) then the**angles**( B und 1 ) contained ... Page 13

13 . from the point B , it can be demonstrated that the

13 . from the point B , it can be demonstrated that the

**angle ABC**together with the angle A , is less than two right angles : therefore any two angles of the triangle are less than two right angles . Cor . If any angle of a triangle be ... Page 14

For in the triangle

For in the triangle

**ABC**the**angle**BAC is acute , ( 1 ) Cor . since BCA is right ( 1 ) , therefore BC is opposite to Prop . 17. the less**angle**, and therefore is less than BA , which ( 2 ) Prop.19 . is opposite to the greater ( 2 ) .### What people are saying - Write a review

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### Common terms and phrases

absurd added alternate angles angle ABC applied arches base bisected centre circle circumference common Constr constructed contained contained in CD continued definition demonstrated described difference divided draw drawn equal equal angles equi-multiples equi-submultiples equiangular equilateral Euclid evident external extremities fall figure fore four magnitudes fourth given line given right line greater half Hence Hypoth inscribed internal join less line AC manner meet multiple oftener parallel parallelogram pass perpendicular placed possible PROB produced Prop proportional proposition proved radius ratio rectangle rectilineal figure remaining right angles right line ruler Schol segment side AC similar squares of AC submultiple taken tangent THEOR third triangle ABC vertex whole

### Popular passages

Page 145 - A plane rectilineal angle is the inclination of two straight lines to one another, which meet together, but are not in the same straight line.

Page 2 - 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 : 16.

Page 28 - To a given straight line to apply a parallelogram, which shall be equal to a given triangle, and have one of its angles equal to a given rectilineal angle.

Page 22 - All the interior angles of any rectilineal figure, together with four right angles, are equal to twice as many right angles as the figure has sides.

Page 118 - A straight line is said to be cut in extreme and mean ratio, when the whole is to the greater segment as the greater segment is to the less.

Page 146 - A plane angle is the inclination of two lines to one another in a plane, which meet together, but are not in the same direction.

Page 168 - The first of four magnitudes is said to have the same ratio to the second, which the third has to the fourth, when any equimultiples whatsoever of the first and third being taken, and any equimultiples whatsoever of the second and fourth ; if the multiple of the first be less than that of the second, the multiple of the third is also less than that of the fourth...

Page 3 - Things which are equal to the same thing are also equal to one another. 2. If equals be added to equals, the wholes are equal. 3. If equals be subtracted from equals, the remainders are equal. 4. Things which coincide with one another are equal to one another.

Page 25 - DE : but equal triangles on the same base and on the same side of it, are between the same parallels ; (i.

Page 3 - A rhombus is that which has all its sides equal, but its angles are not right angles.