. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools, and a hand-book for the use of engineers in field and office . al equation of a parabola passing through the point n (Fig. 36)may be written 2/ + y,!^ = 22?(a; + a;„), y2 y,^ from which ir„ =——\--rr—— x. ^ 2p 2p N . When X =• x^ y Va ^^^ ^^ have The general equation of a tangent passing through the point A may bewritten from whichWhen X = iXg,y = X = vvap ^A. ■■Va [ = = 2/^], and we have , ^a = Vn^AP ■ ^A, o/n = x^- x^== yA^ + Vn- ^VriVj OJh 2v = (VA-Vvy2p Art?2p 2p = va XA Ae .
. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools, and a hand-book for the use of engineers in field and office . al equation of a parabola passing through the point n (Fig. 36)may be written 2/ + y,!^ = 22?(a; + a;„), y2 y,^ from which ir„ =——\--rr—— x. ^ 2p 2p N . When X =• x^ y Va ^^^ ^^ have The general equation of a tangent passing through the point A may bewritten from whichWhen X = iXg,y = X = vvap ^A. ■■Va [ = = 2/^], and we have , ^a = Vn^AP ■ ^A, o/n = x^- x^== yA^ + Vn- ^VriVj OJh 2v = (VA-Vvy2p Art?2p 2p = va XA Ae . • eh .*. »n = A 2 eh -, Ae Tliis proves the general proposition that if secants are drawn parallel tothe axis of x, intersecting a parabola and a tangent to it, the intercepts be-tween the tangent and the parabola are proportional to the square of thedistances (measured parallel to y) from the tangent point. CHAPTER III. OF EXCAVATIONS AND EMBANKMENTS. 88. Usual form of cross-section in cut or fill. The normalform of cross-section in cut is as shown in Fig. 40, in ,g represents the natural surface of the ground, no matter e \. how irregular; ah represents the position and width of the re-quired roadbed; ac and bd represent the side slopes whicl;begin at a and 6 and which intersect the natural surface at such
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Keywords: ., bookauthorwebbwalt, bookcentury1900, bookdecade1920, bookyear1922
