## The Element of Geometry |

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### Common terms and phrases

AC is equal adjacent angles angle ABC angle ACB angle BAC angle DEF arc AC base BC bisect centre circle ABCD circle EFGH coincide described diameter divided drawn duplicate ratio equal 17 equal angles equal circles equal to AC equiangular fore four right angles given straight line gnomon greater half the perimeter homologous sides interior angles join less Let ABC Let the straight opposite angles parallel parallelogram perpendicular polygon PROB produced Q. E. D. Cor Q. E. D. PROP radius rectangle BC rectangle contained rectilineal figure remaining angle right angled triangle secant segment side AC similar sine square of AC straight line AC THEOR touches the circle triangle ABC twice the rectangle wherefore whole angle

### Popular passages

Page 37 - 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 on the line between the points of section, is equal to the square on half the line.

Page 25 - To draw a straight line through a given point parallel to a given straight line. Let A be the given point, and BC the given straight line ; it is required to draw a straight line E iR.

Page 16 - To draw a straight line at right angles to a given straight line, from a given point in the same.

Page 41 - In obtuse-angled triangles, if a perpendicular be drawn from either of the acute angles to the opposite side produced, the square on the side subtending the obtuse angle is greater than the squares on the sides containing the obtuse angle, by twice the rectangle contained by the side...

Page 102 - The circumference of every circle is supposed to be divided into 360 equal parts, called degrees ; and each degree into 60 equal parts, called minutes ; and each minute into 60 equal parts, called seconds ; and these into thirds, &c.

Page 99 - ... magnitudes there be taken more than its half, and from the remainder more than its half, and so on, there shall at length remain a magnitude less than the least of the proposed magnitudes.

Page 13 - If two triangles have two sides of the one equal to two sides of the...

Page 25 - If a side of any triangle be produced, the exterior angle is equal to the two interior and opposite angles; and the three interior angles of every triangle are together equal to two right angles.

Page 76 - 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 31 - If a straight line meet two straight lines, so as to make the two interior angles on the same side of it taken together less than two right angles...