## What initial conditions am I missing?...

I've been writing this code to simulate the orbit of Venus in a simple 2D polar plot, but it keeps telling me that I have insufficient initial conditions, here is the code:

restart:with(Physics):with(VariationalCalculus):with(plots):with(plottools):

R[V] := 0.72*AU: #`starting radius for venus`

AU := 1: #`astronomical unit`

G := 6.674*10^(-11): #`gravitational constant`

m[S] := (333*10^3)*m[E]: #`mass of the sun`

m[V] := 0.815*m[E]: #`mass of venus`

m[E] := 1: #`mass of the earth`

x[V] := t -> r[V](t)*cos(theta[V](t)): #`x-coordinate`

y[V] := t -> r[V](t)*sin(theta[V](t)): #` y-coordinate`

x[VP] := t -> diff(x[V](t), t): #` x-velocity`

y[VP] := t -> diff(y[V](t), t): #`y-velocity`

T[V] := m[V]*simplify(x[VP](t)^2 + y[VP](t)^2)/2: #`kinetic energy of the system`

V[V] := (-G)*m[V]*m[S]*1/r[V](t): #`potential energy of the system`

L[V] := T[V] - V[V]; #`lagrangian of the system`

EL[Vr] := diff(L[V], r[V](t)) - diff(diff(L[V], diff(r[V](t), t)), t) = 0: #` e-l for the r-coordinate`

EL[`Vtheta;`] := diff(L[V], theta[V](t)) - diff(diff(L[V], diff(theta[V](t), t)), t) = 0: #`e-l for the theta-coordinate`

EL[V] := [EL[Vr], EL[`Vtheta;`]]; #` system of equations`

F[V] := G*m[V]*m[S]*1/R[V]^2: #`gravitational force for venus starting position`

omega[V] := sqrt(F[V]*R[V]*1/m[V])*1/R[V]: #`angular velocity for venus starting position`

IC[V] := [r[V](0) = R[V], D(r[V])(0) = 0, theta[V](0) = 0, D(theta[V])(0) = omega[V]]; #`initial conditions, r-position, r-velocity, theta-position, theta-velocity`

SOL := dsolve(EL[V], IC[V], [r[V](t), theta[V](t)], numeric, output = listprocedure); #`numerical solution`

Error, (in dsolve/numeric/type_check) insufficient initial/boundary value information for procedure defined problem

I have included both the initial values for r,dr/dt, theta and dtheta/dt.

I'm not sure what other initial conditions I could be missing?

## Optional Python installation?...

Currently, a stand-alone or embeddable Python is by default bundled with Maple and is installed silently (namely, without notification) when installing Maple, but why is there no prompt panel asking for Python configuration (just like Why does Maple ask for a Matlab installation when I install it? and Configuring the Maple Kernel for Jupyter)?
Actually, I am wondering why I am not capable of installing Maple without bundling Python (even if I am able to clear those files in \$MAPLE/Python.\$SYS later). In my opinion, a bundling Python suite is more or less unnecessary; wouldn't it be better to provide a tooltip asking for approval? If one really need to interact with Python, one may instruct Maple to make use of some available local version of Python from the outset (rather than having to install an additional Python interpreter with numerous extra packages that occupy almost 2 GB!), and if one does not require such a functionality, one can simply skip the Python installation and free up 2GB immediately. So, will installing Python (or another popular external program, if it is going to be integrated or connected with Maple in future releases) be optional during the Maple installation process?

## How to replace a specific list/set entry?...

I am trying to replace thickness = 0 with thickness = 3 in a list, under the condition leader = 0

The order of entries in the list is not fixed so it is more akin to a set.

```leader:=1;

parms:=[colour=red,thickness=0,linestyle =dash];
[op(parms),thickness=3];
display(plottools:-line([1,2], [3,4]),op(parms));
```

## Any way to export a 3D plot to 3D pdf?...

Is there any to export a 3d plot so it could be used as a 3d pdf or some other document type?

 >
 >
 >

## Integration with vectors and units...

 >
 >
 >
 >
 >
 >
 (1)
 >
 (2)
 >
 (3)
 >
 (4)

As you can see in (4) units are wrong. I have tried to insert them in int expression but nothing has work. Moreover using Units[Standard] packecge i get

Error, (in int) wrong number (or type) of arguments: wrong type of integrand passed to indefinite integration.

Thanks

## What am I doing wrong in trying to solve this syst...

Hello. Can anybody point out to me what I am doing wrong below? I'm trying to solve the online model 4.1 of the book "An introduction to infectious disease modelling" by E. Vynnycky & R.G. White (2010). But all the information is below.

Where I get errors from the code below is right at the bottom, in dsolve:

# My Maple 2023 code:

restart;

# Initial values:

Sus_0 := total_popn - Infectious_0 - Immune_0:
Preinfectious_0 := 0:
Infectious_0 := 1:
Immune_0 := total_popn*prop_immune_0:

# Transmission- and infection-related parameters:

preinfectious_period := 8:
infectious_period := 7:
R_zero := 13:
f := 1/preinfectious_period:
r := 1/infectious_period:
beta := R_zero/(total_popn*infectious_period):
prop_immune_0 := 0:

# Demography-related parameters:

total_popn := 100000:

# Useful statistics:

new_infns := beta*Susc*Infe:
new_infectious := Prei*f:
prop_sus = Susc/total_popn:
R_n := R_zero*prop_sus:
propn_imm := 1 - prop_sus:
sum_pop := Susc + Prei + Infe + Immu:
ln_infectious := ln(Infe):
ln_cum_infe := ln(Cum_Infe):
ln_new_infectious := ifelse(0 < t, ln(new_infectious), 0):

# Defining the system of ODEs:

sys_ode:={
diff(Susc(t),t)=-beta*Susc(t)*Infe(t),
diff(Prei(t),t)=beta*Susc(t)*Infe(t)- Prei(t)*f,
diff(Immu(t),t)=Infe(t)*r,
diff(Cum_Infe(t),t)= Prei(t)*f,
diff(Infe(t),t)=Prei(t)*f-Infe(t)*r,
}:

ics:={
Susc(0)=Sus_0,
Infe(0)=Infectious_0,
Immu(0)=Immune_0,
Prei(0)=Preinfectious_0,
Cum_Infe(0)=Infectious_0
}:

Solution1:=dsolve({sys_ode,ics},type=numeric);
# HERE I GET THIS ERROR MESSAGE: "Error, (in dsolve/numeric/process_input) system must be entered as a set/list of

# expressions/equations"

Solution2:=dsolve({sys_ode,ics});
# HERE I GET THIS ERROR MESSAGE: "Error, (in dsolve) invalid arguments; expected an equation, or a set or list of them,

# received: {{diff(Immu(t),t) = 1/7*Infe(t), diff(Infe(t),t) = # 1/8*Prei(t)-1/7*Infe(t), diff(Prei(t),t) =

# 13/700000*Susc(t)*Infe(t)-1/8*Prei(t), diff(Susc(t),t) = -13/700000*Susc(t)*Infe(t), diff(Cum_Infe(t),t) = # 1/8*Prei(t)}}"

MY QUESTION: Can anybody tell me what I'm doing wrong in Solution1 and Solution2?

Best wishes and many thanks!

## Is maplev-mode still supported?...

Ubuntu 22.04.

I have Maple-202[1-3] and an old installation of maplev-mode. maplev-mode fails to work.

In the emacs messages buffer, I see (typed from memory):

maple not running

I removed all of maplev from my system.
make install fails:

> pwd
/tmp/maplev-master
> make install
Makefile:27: MapleLisp.mk: No such file or directory
make: *** No rule to make target 'MapleLisp.mk'.  Stop.

I tried installing from the cloud, but, failed. The error message (even run as root)

Error, (in PackageTools:-Install) permission denied

Will maplev-mode work?

Tom Dean

## Newbiee question - why did algsubs replacement fai...

the maple document is  p151.mw

Hi everyone, I'm trying to do some simple algebraic simplification operations and run into algsubs replacement failures,

the symbol σ' is typed in this way:  σ +  prime (left Palettes -> Common Symbols -> prime) + (selecting σ'  and  press  Ctrl+Shift+A  make it  a  atomic variable)

I'm new to this, any help or suggestion is welcome, thanks!

## How can I get solution of this integral?...

Good day to all of you friends, just asking for your kind help.

I have been trying to get solution of the next integral but didn't have succes. The goal of the code is to perfom a variable change.

Best regards

## Compare the digits of two numbers...

Hello

I would like to compare the digits of two natural numbers p and q first. Then I would like to omit in p and q the digits which they have in common.

Example: p=2345, q=1536

the common digits are 3 and 5. omitted them in both numbers, it will result p'=24 and q'=16.

## how to define a gauge plus coordinate covariant de...

Hello
i am using maple 2023 and the physics package and have the following question:
I want to define a gauge-  plus coordinate covariant derivative i.e.
assuming i,j,k are SO(3) indices and greek indices describe 4-dim space-time (not necessary flat)
i need the following derivative:

D_sigma F_i _rho _lambda = nabla_sigma F_i _rho _lambda + epsilon_i ^j ^k  A_j_sigma  F_k~rho~lambda
with _ meaning lower indices and ^ upper indices and nabla the convenient coordinate covariant derivative of general relativity.
F is a tensor objekt with 2 space time indices and 1 so(3) indices (e.g. Yang Mills field strength) and A is the so(3)gauge potential
How can i define this Differentialoperator with the physics package.
I.e. i want to work with SO(3) Yang-Mills Fields in curved space time and need this generalized Differentialoperator
thanks for helping. I hope its clear from this ascii text in the screen
regards Michael

## Misbehaving plot in Maple 2023...

 > restart;

Here we have a pretty well-behaved trig function:

 > y := t -> 144*cos(t)^6 - 216*cos(t)^4 + 32*cos(t)^3 + 81*cos(t)^2 - 24*cos(t) + 17;

 > plot(y(t), t=0..2*Pi, view=0..35);

Maple 2023 plots  with a strange artifact at :

 > plot(y(t)^(3/2), t=0..2*Pi, view=0..200);

Any reason for that?  Maple 2021 and earlier used to produce the correct plot:

## Textplot "align". Any way af changing it's offset...

Using textplot  is there anything that can be done to to increase the offest of alignI would like to raise  P3 at top of graph up a bit and S3 down. they are {centre, above} and {centre,below}. I know I can tie them to a different point  coordinate to begin with but that is messy to control inside a procedure.

## How to Submit a Workbook package from the MapleClo...

Can I link my MapleCloud application to the Application Center?

Several years ago I uploaded an installable workbook application for Clifford Algebra to the public maplecloud following the guidelines and formats set down in maple help. My intention was to make the application available in the application center, but I just noticed that a package uploaded to MapleCloud is not  available for searching in the Application Center. Unfortunately,the Maple Cloud site for public packages is a mess. One cannot readily browse the applications there like in the application center.

The submissions page for the application center is not helpful in this case. It seems to assume submissions will take the form of maple documents/ worksheets rather than applications written in a workbook). I could not navigate to the Maple Cloud to drop a link to my package using the submission form, but it should be possible to link the the package already installed on the MapleCloud to the Cloud? (Because I is easier to update the MapleCloud package and it can be installed by opening from the Cloud).

## How to display all 4 roots of the Compressible Flo...

Hi there,

I would like this code to display all 4 roots of this equation. I have graphed it in Desmos, so I know it intersects the X-axis in 4 places (the two positive ones representing the subsonic and supersonic Mach number, the negative ones are not needed). However, Maple only shows the subsonic positive and negative values and says that there may be missing solutions. Code and results are provided at the bottom.

I would appreciate any guidance on this issue or with solving this particular equation.

Thank you,

Jack