## Elements of Geometry: Containing the First Six Books of Euclid, with a Supplement of the Quadrature of the Circle and the Geometry of Solids |

### From inside the book

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**common section**of the two planes are perpendicular to the other plane . / III . The inclination of a straight line to a plane is the acute angle contained by that line and another straight line drawn from the point in which the first ... Page 228

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**common section**, at right angles to that line , one line in one plane , and the other line in the other plane . Of the two adjacent angles made by two lines drawn in this manner , that which is acute is also called the inclination of ... Page 230

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**common section**. From B to D draw the straight line BD . Because the points B , D are in the plane AB , the straight ...**common section**of these planes . Therefore , if two planes , & c . Q. E. D. / B C D A PROP . IV . THEOR . Ν ... Page 231

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**common section**of this plane with the plane in which BD and BE are will be a straight linea . Let this line be BF ; a 3.2 . Sup . therefore the three straight lines AB , BC , BF are in one plane , which passes through AB , BC . Because ... Page 236

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**common section**of this with the given plane a 3.2 . Sup . is a straight line passing through Aa . Let DAE be their**common section**; then the straight lines AB , AC , DAE are in one plane . Because CA is at right angles to the given ...### Other editions - View all

### Common terms and phrases

ABC is equal altitude angle ABC angle ACB angle BAC angle contained angle EDF arch base BC bisected Book centre circle ABC circumference coincide common section cylinder definition demonstrated diameter draw drawa equal angles equiangular equilateral polygon equimultiples Euclid exterior angle fore four right angles given circle given straight line greater inscribed interior and opposite join less Let ABC Let the straight meet multiple opposite angle parallelogram parallelogram ABCD perpendicular point F polygon prism PROB produced proportional proposition pyramid Q. E. D. COR Q. E. D. PROP ratio rectangle contained rectilineal figure remaining angle segment solid angle solid parallelepipeds straight line AB straight line AC Suppl THEOR third touches the circle triangle ABC triangle DEF

### Popular passages

Page 121 - 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 42 - 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 63 - Therefore, in obtuse-angled triangles, &c. QED PROP. XIII. THEOREM. In every triangle, the square of the side subtending either of the acute angles is less than the squares of the sides containing that angle, by twice the rectangle contained by either of these sides, and the straight line intercepted between the perpendicular let fall upon it from the opposite angle, and the acute angle.

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 183 - Equiangular parallelograms have to one another the ratio which is compounded of the ratios of their sides. Let AC, CF be equiangular parallelograms having the angle BCD equal to the angle ECG ; the ratio of the parallelogram AC to the parallelogram CF is the same with the ratio which is compounded •f the ratios of their sides.

Page 3 - A diameter of a circle is a straight line drawn through the centre, and terminated both ways by the circumference.

Page 291 - 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 160 - ... extremities of the base shall have the same ratio which the other sides of the triangle have to one...

Page 10 - ... shall be greater than the base of the other. Let ABC, DEF be two triangles, which have the two sides AB, AC, equal to the two DE, DF, each to each, viz.

Page 14 - Therefore, upon the same base, and on the same side of it, there cannot be two triangles that have their sides which are terminated in one extremity of the base equal to one another, and likewise those which are terminated in the other extretnity equal to one another.