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 Author Comment/Response Adam 06/26/10 11:51am Hi, I work on mathematica 7 and I do not know how to plot z1'[t] function. I solve 2 equations and plot solution. sk = NDSolve({L1 /(g*A1)*Q1'[t] == H0 - z1[t] - k*Q1[t]*Abs[Q1[t]], z1'[t] == (Q1[t] - Q2)/As, Q1[0] == Q0, z1[0] == H0 }, {Q1[t], z1[t]}, {t, 0, 10000}]; (*Plot Charts*) Plot[z1[t] /. sk, {t, 0, 5000}, PlotRange -> All, AxesLabel -> {t [s], z1[m]} ] Plot[Q1[t] /. sk, {t, 0, 5000}, PlotRange -> All, AxesLabel -> {t [s], Q1[m^3/s]}] That work fine, and when I try Plot[z1'[t] /. sk, {t, 0, 5000}, PlotRange -> All, AxesLabel -> {t [s], z1[m]} ] The output is just a coordinate system. How to get value of a function? in) z1[10]/.sk out) {z1[10]} Thank You for help. Attachment: Untitled-1.nb, URL: ,

 Subject (listing for 'first derivative from numerical solution') Author Date Posted first derivative from numerical solution Adam 06/26/10 11:51am Re: first derivative from numerical solution yehuda ben-s... 06/27/10 08:41am
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