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Question: ODE system difficulties

Question:ODE system difficulties

Joel Berger 16 Maple
ode differential-equation piecewise dsolve numeric
September 06 2007
0
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. What can I do? Thanks PS. I can provide more detail in the problem if needed, it is a lot to type.
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