## Evaluating expressions inside an Explore command...

Dear Maple users

Let's say I want to plot a line containing a parameter, for example (a+2)*x+6, where a is the parameter. When using the following Explore command:

Explore(plot((a+2)*x+6, x = -5 .. 5, view = -10 .. 10), parameters = [a = -4.0 .. 3], initialvalues = [a = 1])

I will be able to change the value of a by using the slider. The actual value of a is currently displayed as well. Now, However, I want to have the current value of the slope of the line displayed as I move the slider. How is this done? When using a print command inside the Explore command the value of a+2 is not displayed, rather "a+2". Can I use some kind of component?

I hope someone can help.

NB! I constructed this rather doll example, just to make it simple.

Regards, Erik

## how to plot this?...

ode1a := diff(y1(t), t) = round(rhs(odeparm1[1][1]))*y1(t)+round(rhs(odeparm1[1][2]))*y2(t)+round(rhs(odeparm1[1][3]))*y3(t);
ode2a := diff(y2(t), t) = round(rhs(odeparm1[1][4]))*y1(t)+round(rhs(odeparm1[1][5]))*y2(t)+round(rhs(odeparm1[1][6]))*y3(t);
ode3a := diff(y3(t), t) = round(rhs(odeparm1[1][7]))*y1(t)+round(rhs(odeparm1[1][8]))*y2(t)+round(rhs(odeparm1[1][9]))*y3(t);
try
ode1a := diff(y1(t), t) = rhs(odeparm1[1][1])*y1(t)+rhs(odeparm1[1][2])*y2(t)+rhs(odeparm1[1][3])*y3(t);
ode2a := diff(y2(t), t) = rhs(odeparm1[1][4])*y1(t)+rhs(odeparm1[1][5])*y2(t)+rhs(odeparm1[1][6])*y3(t);
ode3a := diff(y3(t), t) = rhs(odeparm1[1][7])*y1(t)+rhs(odeparm1[1][8])*y2(t)+rhs(odeparm1[1][9])*y3(t);
sys := DiffEquation([ode1a, ode2a, ode3a], inputvariable = [y1(t)], outputvariable = [y2(t), y3(t)]);
sysz := ToDiscrete(sys, ts); in_t := Sine(1, 1, 0, 0);
sol := Simulate(sys, [in_t]);
try
p1 := plots[odeplot](sol, [[t, y2(t)]], t = 0 .. t_sim, numpoints = 200, color = red);
print("succeed 1 2", i)
catch:
print("error draw at ", i)
end try;
try
p1 := plots[odeplot](sol, [[t, y3(t)]], t = 0 .. t_sim, numpoints = 200, color = red);
print("succeed 1 3", i)
catch:
print("error draw at ", i)
end try
catch: print("error at ", i);
print(lastexception);
print(ode1a);
print(ode2a);
print(ode3a);
end try;
try
ode1a := diff(y1(t), t) = rhs(odeparm1[1][1])*y1(t)+rhs(odeparm1[1][2])*y2(t)+rhs(odeparm1[1][3])*y3(t);
ode2a := diff(y2(t), t) = rhs(odeparm1[1][4])*y1(t)+rhs(odeparm1[1][5])*y2(t)+rhs(odeparm1[1][6])*y3(t);
ode3a := diff(y3(t), t) = rhs(odeparm1[1][7])*y1(t)+rhs(odeparm1[1][8])*y2(t)+rhs(odeparm1[1][9])*y3(t);
sys := DiffEquation([ode1a, ode2a, ode3a], inputvariable = [y2(t)], outputvariable = [y1(t), y3(t)]);
sysz := ToDiscrete(sys, ts);
in_t := Sine(1, 1, 0, 0);
sol := Simulate(sys, [in_t]);
try
p1 := plots[odeplot](sol, [[t, y1(t)]], t = 0 .. t_sim, numpoints = 200, color = red);
print("succeed 2 1", i)
catch:
print("error draw at ", i)
end try;
try
p1 := plots[odeplot](sol, [[t, y3(t)]], t = 0 .. t_sim, numpoints = 200, color = red);
print("succeed 2 3", i)
catch:
print("error draw at ", i)
end try
catch:
print("error at ", i);
print(lastexception);
print(ode1a);
print(ode2a);
print(ode3a)
end try;
try
ode1a := diff(y1(t), t) = rhs(odeparm1[1][1])*y1(t)+rhs(odeparm1[1][2])*y2(t)+rhs(odeparm1[1][3])*y3(t);
ode2a := diff(y2(t), t) = rhs(odeparm1[1][4])*y1(t)+rhs(odeparm1[1][5])*y2(t)+rhs(odeparm1[1][6])*y3(t);
ode3a := diff(y3(t), t) = rhs(odeparm1[1][7])*y1(t)+rhs(odeparm1[1][8])*y2(t)+rhs(odeparm1[1][9])*y3(t);
sys := DiffEquation([ode1a, ode2a, ode3a], inputvariable = [y3(t)], outputvariable = [y1(t), y2(t)]);
sysz := ToDiscrete(sys, ts);
in_t := Sine(1, 1, 0, 0);
sol := Simulate(sys, [in_t]);
try
p1 := plots[odeplot](sol, [[t, y1(t)]], t = 0 .. t_sim, numpoints = 200, color = red);
print("succeed 3 1", i)
catch:
print("error draw at ", i)
end try;
try
p1 := plots[odeplot](sol, [[t, y2(t)]], t = 0 .. t_sim, numpoints = 200, color = red);
print("succeed 3 2", i)
catch:
print("error draw at ", i)
end try
catch:
print("error at ", i);
print(lastexception);
print(ode1a);
print(ode2a);
print(ode3a)
end try

diff(y1(t), t) = 1.052936200*10^5*y1(t)+70106.19000*y2(t)+35169.00000*y3(t)
diff(y2(t), t) = 70106.19000*y1(t)+71031.61000*y2(t)+35511.00000*y3(t)
diff(y3(t), t) = 35169.00000*y1(t)+35511.00000*y2(t)+36100.00000*y3(t)
"the DEs contain functions with undefined values (probably caused by a discontinuity in the input that was differentiated). As a result, the numerical solution cannot be calculated. The DE system is: %1\"",[(&DifferentialD;)/(&DifferentialD;t) y1(t)=1.052936200 10^5 y1(t)+70106.19000 y2(t)+35169.00000 ({[[0,t<0],[sin(t),otherwise]]),(&DifferentialD;)/(&DifferentialD;t) y2(t)=70106.19000 y1(t)+71031.61000 y2(t)+35511.00000 ({[[0,t<0],[sin(t),otherwise]]),{[[0,t<0],[undefined,t=0],[cos(t),0<t]]=35169.00000 y1(t)+35511.00000 y2(t)+36100.00000 ({[[0,t<0],[sin(t),otherwise]]),y2(0)=0,y1(0)=0]

it has error when plot

## Maple Cloud recognizes my MaplePrimes login creden...

None of those things is true. Using those same credentials, I am able to log in to Maple Cloud in my office but not from home.

Has anyone else had this problem or know of a solution?

Thanks!

Running Maple 2017 in office on Windows 7 and at home on Windows 10.

Office copy is through a site license purchased by my university. Home copy is a personal home-use copy obtained through the Maple Adoption program.

## error in dsolve.....

I have a problem for converging dsolve?

"matrix is singular" and '"initial Newton iteration is not converging"'

thanks

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## Maple Interactive Worksheet...

I am attempting to build a text field at the bottom of this worksheet MathApps-ResistorsMark.mw  that asks users for the resistance.

I am hoping to have the value of the text field evaluated using the Module() at the bottom of the startup code, for use as a question within MapleTA.  For some reason I can get the code to work for a slider, but not a textbox.

I have limited knowledge about startup code.

Notice: I will be removing the resistance from the diagram for students after I know it works.

I appreciate any help that can be offered.

## What actions after an event? (ODE numeric events)...

I am trying to understand the use of "events" in solving ode's, specifically the possible actions.
From the help pages:

Events are specified by the events=[event1,event2,...] option in the call to dsolve[numeric], where each event is a list of [trigger,action] pairs, where the trigger describes the trigger of the event, and the action describes the action to perform when the event is triggered.

It then goes on to list possible actions, for example,

u(t) = -u(t): execute statement when triggered
â [u(t) = -u(t), y(t) = -y(t)]: execute statements when triggered
[If(y(t) < 0, y(t) = -y(t), halt)]: execute statements conditionally when triggered

I tried to use the first one unsuccessfully several ways:
This works:dsolve({eq, y(0) = 1, (D(y))(0) = -1}, numeric, events = [[x+y(x) = 15, halt]])

but dsolve({eq, y(0) = 1, (D(y))(0) = -1}, numeric, events = [[y(x) = 0,[ 'print("Yes'")', halt]]]) does not

nor does any variant of that using print.

Also, I cannot get at the result of any assingment, e.g.,

dsolve({eq, y(0) = 1, (D(y))(0) = -1}, numeric, events = [[y(x) = 0, [z = diff(y(x), x), halt]]]) does not work either; z does not have a value. What commands can be executed as actions after an event is triggered?

## Issue with 3d plot...

I experience an issued with a 3d plot. This is my code and I get: "Warning, expecting only range variables [H[s], H[j]] in expression eq to be plotted but found name eq." as a return from Maple.

restart;

eq = c[1]-abs(H[s])^2*sigma^2/abs(H[j])^2;

c[1] := 2;

c[2] := 4;

sigma := 1;

tmp := plot3d(eq, H[s] = .1 .. 2, H[j] = 0 .. 5, view = 0 .. 8,

axes = boxed, labels = [H[s], H[j], P[j]],

filled = [style = surface, transparency = .2]); plots:-display(tmp, view = 0.1e-1 .. 8)

## Difference between two form of eigenvalue problem?...

I have two square matrices (LS,RS) in the form of generalized eigen-value problem as below:

LS*z=omega*RS*z

One time, I am using inverse of RS multiplying by LS to get the eigen values as
MS := MatrixInverse(RS) . LS:
VL1, VR1 := Eigenvectors(MS):

Next time, I am using direct method as below to get the eigen values

VL2, VR2 := Eigenvectors(LS, RS);

I am wondering there are meaningful differences between VL1 and VL2 as well as VR1 and VR2.

Does anybody know why?

RS.mw

LS.mw

## An issue with mapleprimes.com...

there is a problem with users tab and web page of mapleprimes, and it just does display the first page and not other pages ...
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https://www.mapleprimes.com/users/?page=2
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i have started using maple toolbox on MATLAB and i have alot of questions...
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for example, i used fsolve , and want output and the calculations be done using 50 Digits, but it does not ! :(

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The object in the above display consists of a thin red disk and attached thin blue disk. They have radii 1.0 and 0.2 and masses 1.0 and 0.2 respectively.

Starting from rest at the above position they are given an initial angular velocity of Omega radians/second which starts the object rolling along the positive x axis.

If Omega is great enough that, at some time during the roll, the vertical component of the centrifugal force on the blue disk exceeds the downward force of gravity on the object, will the object begin a spinning projectile motion above the x axis?

Assuming both disks have negligible thickness, what Physics laws will govern the rolling and (possible) spinning projectile motions and what mathematics describes these motions?

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For example, suppose only the 111,181, 206th elemenst of this vector are positive values as: 101.2109e11,19211.129,87211.

How to get both 111,181, 206 and their corresponding values, 101.2109e11,19211.129,87211?

## solving Ax=b, where A contains one symbol in MAPL...

Dear Maple users,

I am solving a system of linear equations Ax=b where A is a matrix (243*241) which contains a rational polynomial of unknown "kappa" along with floating numbers. As suggested in some other posts I am using Linear algebra package with the LinearSolve command and option "solve" to find out unknown vector x. b is a vector having entries zero and 1. The system is such that two equations are redundant but it is difficult to recognise which two are redundant and hence for the time being I am keeping them in the matrix. (For a known value of kappa (say kappa=2) I have checked that two equations are redundant.) For the reference, the matrix and the right-hand vector b is attached as text.

There are two issues

1) Maple takes very long time (12 hours and so) to get x=b\A;

2) The result is a long expression i.e.  x[i] is a rational polynomial in kappa; a very long rational polynomial which I am importing as a text. I am not sure if maple exports all terms in the polynomial as for the different value of kappa I see Ax-b >0.

How can I overcome this problem? Any help will be greatly appreciated.

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