jing

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10 years, 251 days

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These are questions asked by jing

Dear All,

I solve an equation  as follows,

m:=dsolve({T(0) = 300, diff(T(t), t) = (min(G1, G2)-Loss)*(1/35513)}, T(t), numeric)

G1,G2, and Loss are functions of T and G1 and Loss are tangent at point A where T=600, when I want to plot the dsolve solution by odeplot,like this

odeplot(m, [t, T(t)], 0 .. 800)]

I got a curve whose maximum value  is  600( equal to the tangent value) and actually the value should increase after passing the tangent point, Who can tell me where is the problem. Thanks.

HI, dear all. When I tried to use the plot option 'adaptive' to make my plot more smooth and realistic, I encountered the following erro. I cannot understand why. From the help guide, I learn that adaptive can be assigned n or true or false, but errors appeared.  Thanks for your help.

 

> implicitplot(-x^3+3*x+a = 0, a = -3 .. 3, x = -4.0 .. 4.0, view = [-3 .. 3, -4 .. 4], adaptive = 2, resolution = 1000, numpoints = 2000);
Error, (in plot/options2d) unexpected option: adaptive = 2
> help("adaptive");

I set a physical model for my reseach,

equ1 := x^4-5*x

equ2 := 1/x+x^2+3

x is a function of time t and it meets diff(x(t), t) = equi-equ2.

I want to plot the curve of x(t) varying with time

When I use the following command

DEplot({x(0) = 0, diff(x(t), t) = equi-equ2},x(t), t = 0 .. 20)   it shows: Error, (in DEtools/DEplot) called with too few arguments

Who can tell me what is wrong with my calculation? Thanks

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