The First Six Books of the Elements of Euclid: With Notes |
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Page 1
... angle is the inclination of two right See N. lines to one another , which meet together , but are not Fig . 2 . in ... ( ABC and ABD ) equal to one another , each of these angles is called a right angle ; B Fig . 4 . Fig . 4 . See N.
... angle is the inclination of two right See N. lines to one another , which meet together , but are not Fig . 2 . in ... ( ABC and ABD ) equal to one another , each of these angles is called a right angle ; B Fig . 4 . Fig . 4 . See N.
Page 2
... angle ( ABC ) , which is greater than a right angle , is called obtuse . 13. The angle ( ABD ) , which is less than a right angle , is called acute . 14. A plane figure is a plane surface , which is bound- ed on all sides by one or more ...
... angle ( ABC ) , which is greater than a right angle , is called obtuse . 13. The angle ( ABD ) , which is less than a right angle , is called acute . 14. A plane figure is a plane surface , which is bound- ed on all sides by one or more ...
Page 6
... ABC , the triangles themselves must coincide , and are therefore equal ( 3 ) . PROP . V. THEOR . In an isosceles ... angle A is common to both , therefore the angle ACF is equal to ABG , and the angle AFC to AGB ; and the side FC is ...
... ABC , the triangles themselves must coincide , and are therefore equal ( 3 ) . PROP . V. THEOR . In an isosceles ... angle A is common to both , therefore the angle ACF is equal to ABG , and the angle AFC to AGB ; and the side FC is ...
Page 8
... triangle be within the other : produce the sides AC and AD , and join CD . Because the ... angle BDC has been proved to be greater than BCD , which is absurd ... ( ABC and EFD ) have two sides of the one respectively equal to two sides of ...
... triangle be within the other : produce the sides AC and AD , and join CD . Because the ... angle BDC has been proved to be greater than BCD , which is absurd ... ( ABC and EFD ) have two sides of the one respectively equal to two sides of ...
Page 13
... 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 obtuse or right , the other two angles are acute : and ...
... 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 obtuse or right , the other two angles are acute : and ...
Common terms and phrases
absurd AC and BD AC and CB AC is equal angle ABC angle ACD angle BAC angle equal base bisected centre circumference Constr constructed contained in CD demonstrated described double the rectangle double the square drawn equal angles equal to AC equal to double equi equi-multiples equi-submultiples equiangular Euclid evident external angle fore form one right four magnitudes proportional four right angles fourth given angle given circle given line given right line given triangle gles half a right Hypoth inscribed less line CD manner multiple oftener opposite parallel parallelogram perpendicular PROB produced Prop proposition radius rectangle under AC right angles right line AB Schol segment side AC sides AB similar squares of AC submultiple taken tangent THEOR third tiple triangle ABC vertex
Popular passages
Page 147 - 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 3 - Things which are equal to the same thing are equal to one another. 2. If equals be added to equals, the wholes are equal. 3. If equals be taken from equals, the remainders are equal. 4. If equals be added to unequals, the wholes are unequal. 5. If equals be taken from unequals, the remainders are unequal. 6. Things which are double of the same are equal to one another.
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 16 - If two triangles have two sides of the one respectively equal to two sides of the other, and the contained angles supplemental, the two triangles are equal.
Page 148 - 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 2 - A diameter of a circle is a straight line drawn through the centre, and terminated both ways by the circumference.
Page 92 - F) a ratio compounded of the ratios which the first has to the second, the second to the third, the third to the fourth (A to D, D to C, and C to F) ; and so on to the last.
Page 93 - AXIOMS. 1. Equimultiples of the same, or of equal magnitudes, are equal to one another. 2. Those magnitudes, of which the same or equal magnitudes are equimultiples, are equal to one another. 3. A multiple of a greater magnitude is greater than the same multiple of a less. 4. That magnitude, of which a multiple is greater than the same multiple of another, is greater than that other magnitude.
Page 25 - DE : but equal triangles on the same base and on the same side of it, are between the same parallels ; (i.
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.