The elements of Euclid: with dissertations intended to assist and encourage a critical examination of these elements as the most effectual means of establishing a juster taste upon mathematical subjects than that which at present prevails, Volume 1
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ABCD accidentally happen adjacent angles angle ABC angle ACB angle BAC angle contained angle EDF angle equal base BC BC is equal Book certainly circle ABC circumference common notion consequences const cut in halves demonstrated described diameter double drawn parallel equal angles equal straight lines equiangular equimultiples Euclid exceed the multiple faid fame manner fame multiple fame parallels fame ratio fame reason fore fourth given circle given straight line Gnomon greater ratio joined less Let ABC let the angle let the straight parallelogram perpendicular point F PROP proportionals proposition reader rectangle contained remaining angle remaining sides right angles segment sides equal squares of AC straight line BC suppose supposition third tiple touches the circle triangle ABC triangle DEF wherefore the angle whole
Page 3 - Let it be granted that a straight line may be drawn from any one point to any other point.
Page 68 - If a straight line drawn through the centre of a circle bisect a straight line in it which does not pass through the centre, it shall cut it at right angles : and if it cut it at right angles, it shall bisect it.
Page 45 - ABG ; (vi. 1.) therefore the triangle ABC has to the triangle ABG the duplicate ratio of that which BC has to EF: but the triangle ABG is equal to the triangle DEF; therefore also the triangle ABC has to the triangle DEF the duplicate ratio of that which BC has to EF. Therefore similar triangles, &c.
Page 15 - When a straight line set up on a straight line makes the adjacent angles equal to one another, each of the equal angles is right, and the straight line standing on the other is called a perpendicular to that on which it stands.
Page 86 - When you have proved that the three angles of every triangle are equal to two right angles...
Page 88 - EA : and because AD is equal to DC, and DE common to the triangles ADE, CDE, the two sides AD, DE are equal to the two CD, DE, each to each ; and the angle ADE is equal to the angle CDE, for each of them is a right angle ; therefore the base AE is equal (4.
Page 42 - If four straight lines be proportionals, the rectangle contained by the extremes is equal to the rectangle contained by the means ; And if the rectangle contained by the extremes be equal to the rectangle contained by the means, the four straight lines are proportionals. Let the four straight lines, AB, CD, E, F, be proportionals, viz.
Page 109 - Draw two diameters AC, BD of the circle ABCD, at right angles to one another; and through the points A, B. C, D, draw (17.