Euclid's Elements of geometry [book 1-6, 11,12] with explanatory notes; together with a selection of geometrical exercises. To which is prefixed an intr., containing a brief outline of the history of geometry. By R. Potts. [With] Appendix
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altitude base bisected Book centre chord circle circle ABCD circumference common cone construction cylinder definition demonstrated described diagonals diameter difference divided double draw drawn equal equal angles equiangular equimultiples Euclid extremities fall figure formed four fourth Geometry given circle given line given point given straight line greater half Hence inscribed intersection join less line drawn magnitudes manner means meet multiple opposite sides parallel parallelogram pass perpendicular plane polygon position problem produced Prop properties proportional PROPOSITION proved pyramid radius ratio reason rectangle contained regular remaining respectively right angles segment semicircle shew shewn sides similar solid sphere square straight line taken tangent THEOREM third touch triangle ABC twice vertex vertical wherefore whole
Page 56 - 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 of the line between the points of section, is equal to the square of half the line.
Page 26 - Wherefore, if a straight line, &c. QED PROPOSITION XXIX. THEOREM. Jf a straight line fall upon two parallel straight lines, it makes the alternate angles equal...
Page 99 - The angle in a semicircle is a right angle ; the angle in a segment greater than a semicircle is less than a right angle ; and the angle in a segment less than a semicircle is greater than a right angle.
Page 15 - The angles which one straight line makes with another upon one side of it, are either two right angles, or are together equal to two right angles. Let the straight line AB make with CD, upon one side of it, the angles CBA, ABD : these shall either be two right angles, or shall together be equal to two right angles. For...
Page 60 - If the vertical angle of a triangle be bisected by a straight line which also cuts the base, the rectangle contained by the sides of the triangle is equal to the rectangle contained by the segments of the base, together with the square on the straight line which bisects the angle.
Page 22 - IF two triangles have two sides of the one equal to two sides of the...
Page vi - The sluggard is wiser in his own conceit than seven men that can render a reason.
Page 54 - If there be imo straight lines, one of which is divided into any number of parts; the rectangle contained by the two straight lines, is equal to the rectangles contained by the undivided line, and the several parts of the divided line.