Author 
Comment/Response 
Jason Parks

11/22/99 6:42pm
I am having a problem solving a system of differential equations and an equation dependent on the differnetial equations. The equations are of the form x'' = a*y'' + b*y'*x' +c*cosx*(y'^2)
y'' = d*x'' + e*sinx*(x'^2) + f*sin(x + y)
F= g*x' + h*y'' + j*(x' + y')^2
these are not the real equations I am trying to solve but they give the idea. F is dependent of the differential equations for x and y. I can use NDSolve() to find x and y interms of time, but I can not solve for F interms of time also. If I put F into the NDSolve() with x and y I am given an error that F is not a differential equation. If I solve for F outside NDSolve I don't know what the values of x and y along with their derivitives are. How can I find F interms of time? Thank you for the help
Jason Parks
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