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Hnx

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7 years, 68 days
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rkf45...

Hnx 20
June 06 2020
0 0

@Giorgios, Preben

Thank you very much to the two of you. I must look into the matter next monday. It is already late here in Switzerland.

Best regards   Heinz

Difficult ODEsys...

Hnx 20
June 06 2020
0 0

Thank you very much, Giorgios! This mistake of mine was stupid. It happened because the code I posted is a portion of a larger file and in this larger file the plot-call figures in the first line. With copy-paste it went forgotten.

ODEplot works fine now. I am continuing with my work.

Question: I would like to look into the code of 'rkf45' in order to add a break condition. Why does the following not work?

 

restart; with(VariationalCalculus); with(PDETools); interface(verboseproc = 2); print(x_rkf45)

x_rkf45

 (1)

``


 

Download Befehle_interface_verboseproc_print_2020-06-06.mw

With 'sin' it works.

Regards Heinz

correction...

Hnx 20
May 28 2020
0 0

Hi Rouben! Thank you very much for your hint! Just learned a thing more about wonderful Maple. Regards   Heinz

Answering "Reply versus Answer...

Hnx 20
May 27 2020
0 0

@acer Hi acer! Thank you for the hint which I will heed of course. This is my first day in the forum and I still have much to learn.  Heinz

Some typos...

Hnx 20
May 27 2020
0 0

Tom, you have been a great help for me. Thank you so much! I have wondered where the additional argument (t) comes from, see below. When composing the ODE (4) all of a sudden there appears phi1(t)(t) instead of phi1(t). This is the reason why it did not work (apart from the undeclared variable g which you found. I cannot explain this. Can you? By the way, it already happens with the command subs, see arcsin.
 

Trebuchet, Phase I, 2020-05-27 Ki

 

restart; with(RealDomain); assume(h < r1); additionally(h < r2)

hz1 := g*(r3*m3*cos(phi1(t))-r1*m2*sin(phi2(t))/sin(phi2(t)-phi1(t)))/theta3

g*(r3*m3*cos(phi1(t))+r1*m2*sin(phi2(t))/sin(-phi2(t)+phi1(t)))/theta3

 (1)

hz2 := phi1(t)+arcsin((h+r1*sin(phi1(t)))/r2)

phi1(t)+arcsin((h+r1*sin(phi1(t)))/r2)

 (2)

hz3 := subs(phi2 = hz2, hz1)

g*(r3*m3*cos(phi1(t))+r1*m2*sin((phi1(t)+arcsin((h+r1*sin(phi1(t)))/r2))(t))/sin(-(phi1(t)+arcsin((h+r1*sin(phi1(t)))/r2))(t)+phi1(t)))/theta3

 (3)

deq := diff(phi1(t), t, t)-hz3 = 0

diff(diff(phi1(t), t), t)-g*(r3*m3*cos(phi1(t))+r1*m2*sin((phi1(t))(t)+(arcsin((h+r1*sin(phi1(t)))/r2))(t))/sin(-(phi1(t))(t)-(arcsin((h+r1*sin(phi1(t)))/r2))(t)+phi1(t)))/theta3 = 0

 (4)

 

NULL


 

Download Unerwartete_(t)_wenn_subs-Befehl_2020-05-27.mw

tomleslie 6232 , reluctant ODE...

Hnx 20
May 27 2020
0 0

Tom, thank you so much! As you can see, your hint came handy. Unfortunately my ODE is more complicated, see below. When dsolve is executed I get the following error message which I do not understand:

Error, (in dsolve/numeric/process_input) system must be entered as a set/list of expressions/equations

Is my syntax wrong? Where?

Additional question: Why don't you use 2D-math?

Regards  Heinz

 


 


 

restart; with(plots)

deq := diff(phi1(t), t, t)-g*(r3*m3*cos(phi1(t))+r1*m2*sin((phi1(t))(t)+arcsin((h+r1*sin(phi1(t)))/r2))/sin(-(phi1(t))(t)-arcsin((h+r1*sin(phi1(t)))/r2)+phi1(t)))/theta3 = 0

deq_numeric := subs(r1 = 8, r2 = 8, r3 = 1, h = 5, m2 = 1, m3 = 20, theta3 = 20, deq)

ics_numeric := phi1(0) = 0, (D(phi1))(0) = -.63

hz1 := dsolve({ics, deq_numeric}, phi1(t), numeric)

``


 

Download Kondensierte_Form_Phase_I_2020-05-27.mw

Answer to "Respect"...

Hnx 20
May 27 2020
0 0

@Carl Love I did not want to be disrepectful and was myself very unhappy how my Maple code was represented! But I did not find a way to copy the code into the window. If there is a way to do it please advice. Regards  Heinz

PS. This is my first time that I use this forum.

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