. An encyclopaedia of architecture, historical, theoretical, & practical. New ed., rev., portions rewritten, and with additions by Wyatt Papworth. nd make BF equal to BC. Join FD and and FE in the .same proportion, or i. into the same number of equal parts. Letthe divisions be numbered from D to F,and from F to E, and join every twocorresponding points by a straight line ;then tlie intersection of all the straightlines will form the parabola required. 1 i06. Prob. IV. To draw a straight line from a given point in the curve of a parabola,u-hich shall be a tangent to the curve at
. An encyclopaedia of architecture, historical, theoretical, & practical. New ed., rev., portions rewritten, and with additions by Wyatt Papworth. nd make BF equal to BC. Join FD and and FE in the .same proportion, or i. into the same number of equal parts. Letthe divisions be numbered from D to F,and from F to E, and join every twocorresponding points by a straight line ;then tlie intersection of all the straightlines will form the parabola required. 1 i06. Prob. IV. To draw a straight line from a given point in the curve of a parabola,u-hich shall be a tangent to the curve at thatpoint. Let DC {fig. 456.) be the double or-dinate, cB the abscissa to the paraboliccurve DBC, and let it be required todraw a tangent from the point e in thecurve. Draw e/parallel to DC, cutting Fi;;.456. BC in /: produce cB to g, and make Rg equal to B/, and join ge, then will ge l)e tlietangent required. In the same manner DII will be found to be a tangent at D. If cKbe drawn perpendicular to the tangent <?«, then will eK be also perpendicular to the curve,and in the proper direction for a joint in the masonry of a parabolic
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