Wentworth, G. A. (George Albert), 1835-1906 · Boston, Ginn & company · leaf 244
RAILROAD CURVES. 71 of curvature will depend on the angle A and the tangent AD.For, in the right triangle ADC, tan 2X4 C=Hence, r- ——-, or tan + ^1 = —AD 2 t t tan-J J.. First Method, … To Lay out the Curve. Let Dm (Fig. 53) represent a portion of thetangent. It is required to find mP, theperpendicular to the tangent meeting thecurve at P. mP=Dn = CD-Cn. CD = r, _Cn = ^CPi= Vr^~ Jff ■f. Fig. 53. Hence, mP^r-Vr2-*2.
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