( 28J ) 

 transforms itself into tiie simpler one 



It is easv to find 



2A, 



The coordinates >, ?^ and ?ofan arbitrary point Q im (lie developable 

 belonginii' to (' can be expressed in the parameters t and /• where 

 )' represents the distance from [)oinl (^ (5, t], $) to point {.i\ //, 2) 

 of the cnspidal cnrve measnred along the tangent of 6' passing throngh 

 Q. The coordinates of Q are : 



dt dx 



% =z= X -\-r , 



ds dt 



dt dy 



ds dt 



dt dz 



^ ds^ dt 



For the points (2 situated in the osculating plane s = the relation 



dt dz 



' ds dt 



must exist betweeji the parameters y and /. Ry eliminating ;• out of 

 this relation and the e(piations for $ and t^ we tijul expressed in 

 functions of t the coordinates of the points Q situated in the plane 

 ? = 0. These coordinates of the points of the curve of intersection 

 d ai'e 



dx dz 



dy dz 



'' ^ dt ' dt 



or 



(c/ + c/ + ...)K-f2«,H...) 2 



, = .... + K t^ + ... - i^£±^±dE,^±l^^l±::l ^ 1 , ,^ ... . 



As here loo is ('(nial to lor / = we lind as aboxe that the 



lit 



I'adius of curvatui'i' /•„ in point I* of llic curxc' d is: 



'/ 5-' 



19* 



