Hello all, you were very helpful the last time I had a question, I hope you can help me again here. I have a system of differential equations that can be manipulated in two way, each has its own problems 1) I can define the system of equations including a piecewise function. The test of the piecewise involves the ratio st(t)/sz(t) being relative to 1. When I attempt to dsolve,numeric this formalism it gives me an error that it cannot convert to an explicit first-order system (not that I asked it to convert by the way). 2) In place of the piecewise I can have int(1/(1+sqrt(st(t)/sz(t))*sin(theta)),theta=0..Pi) which should evaluate to a real number, and is incidentally where the piecewise function comes from. However then dsolve tells me that it cannot have an integral in a differential equation.

Hello all, I know several people around my university that have had this problem so I finally thought I should ask: Lets say I have some complicated integral, the integrand is a function of several variables. If I: 1)simply evaluate it and I get some function of the remaining variables. 2)try to assign it such as A:=(x,y,z)-> integral, I get A(x,y,z)=integral what I want is to first evaluate to a function and then assign that function as some name as a function of the remaining variables. I know this must be possible, but I can't seem to get it. Thanks for the help. (I can provid