THEORY OF COMPONUD CURVES IN FIELD ENGINEERING 



149 



Let the tangent-distance of the other branch of the compound curve 

 be NT = NP = NR = S, Fig. 5. Assume the direction of the tangent 

 T 1 , = IC as the ;y-axis, and the perpendicular to it at the point of curve 



Fig. 5 



C as the x-axis. Then for the co-ordinates a and b of T in (17) we have, 



since IC = 7\, IT = T 2 



a== T 2 sin </>, 



b =T t + T 2 cos <f>. 



According to usage, we designate by <f> the angle supplementary to 



the angle formed by the tangents and opposite the compound curve. 



