Re: Solving difficult integral

*To*: mathgroup at smc.vnet.net*Subject*: [mg18895] Re: Solving difficult integral*From*: "Christian Gudrian" <Christian.Gudrian at hermes.kawo1.rwth-aachen.de>*Date*: Mon, 26 Jul 1999 14:27:42 -0400*Organization*: Aachen University of Technology / Rechnerbetrieb Informatik*References*: <7mek2g$9il@smc.vnet.net> <7mjr6q$f3k@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Paul Abbott <paul at physics.uwa.edu.au> schrieb in im Newsbeitrag: 7mjr6q$f3k at smc.vnet.net... > The real question is why do you need the general solution and, if you > have it, what do you want to do with it? (: Hi, Paul! Well, what am I trying to do? I want to write a C-program which does the following: I've got four points in R3 which define one section of a Catmull-Rom-Spline. With the coordinates of these four points I get a formula P(t) (0 <= t <= 1) which defines the curve between point two and thre (the points one and four are needed to calculate the tangents through the curve at points two and three). If I now wished (well, I certainly do!) to know the length of the path my point P(t) left behind at a certain point of time t I need to integrate the value of the velocity vector Sqrt[(dP/dt)^2] with the limits 0 and t to get a function s(t). But my core problem is even more complicated: I need the inverse function t(s) basically. What makes the whole situation even more complicated is that I do not know neither of the variables in advance. Right know I'm thinking about using MathLink to do the respective calculations during runtime when all things a definite. This should FullSimplify[Everthing] (: Greetings from Germany, Christian