How to get first-order optimality from scipy.optimize module

If I have this equation f(v,R,xi)=2/v*((((((v*t0/2)+R))*2+((xi-x0)*2))**0.5)-R).

How to 开发者_如何学JAVAget the first-order optimality from that equation when I use that equation to get min v,R using scipy.optimize.leastsq ?

I don't have problem to get min v,R using scipy.optimize.leastsq but I get confused when I want get first-order optimality...

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