# Question:How do I plot a combination of variables using phaseportrait of DEtools?

## Question:How do I plot a combination of variables using phaseportrait of DEtools?

Maple 2020

Hi, I am doing a project about three body problem. I am solving a DE system with 12 DEs and plotting it with phase portrait. It is all good if I am only using vars in scene. like this:

pp1 := phaseportrait([eq1(t), eq2(t), eq3(t), eq4(t), eq5(t), eq6(t), eq7(t), eq8(t), eq9(t), eq10(t), eq11(t), eq12(t)], [x1(t), y1(t), vx1(t), vy1(t), x2(t), y2(t), vx2(t), vy2(t), x3(t), y3(t), vx3(t), vy3(t)], t = 0 .. 8.75*10^7, [[x1(0) = X1, y1(0) = Y1, vx1(0) = VX1, vy1(0) = VY1, x2(0) = X2, y2(0) = Y2, vx2(0) = VX2, vy2(0) = VY2, x3(0) = X3, y3(0) = Y3, vx3(0) = VX3, vy3(0) = VY3]], scene = [x1(t), y1(t)], stepsize = 1000, x1 = 0 .. 10^6, y1 = 0 .. 6*10^6, color = [red], scaling = constrained):

But I cannot plot any combinations of my variables. I have orthogonalized all the velocity, and I can plot [t,vx(t)] or [t, vy(t)]. But I cannot plot [t, (vx(t)^2+vy(t)^2)^1/2]:

vel1 := phaseportrait([eq1(t), eq2(t), eq3(t), eq4(t), eq5(t), eq6(t), eq7(t), eq8(t), eq9(t), eq10(t), eq11(t), eq12(t)], [x1(t), y1(t), vx1(t), vy1(t), x2(t), y2(t), vx2(t), vy2(t), x3(t), y3(t), vx3(t), vy3(t)], t = 0 .. 3.5*10^7, [[x1(0) = X1, y1(0) = Y1, vx1(0) = VX1, vy1(0) = VY1, x2(0) = X2, y2(0) = Y2, vx2(0) = VX2, vy2(0) = VY2, x3(0) = X3, y3(0) = Y3, vx3(0) = VX3, vy3(0) = VY3]], scene = [t, (vx3(t)^2 + vy3(t)^2)^(1/2)], stepsize = 1000, linecolor = [purple], scaling = constrained);
Error, (in DEtools/phaseportrait) Invalid scene; must be list of vars: scene = [t, (vx3(t)^2+vy3(t)^2)^(1/2)]

Is there a way to let me plot the v(t) ?

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