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?

i am facing problem while solving differential equation in loops where conditons are given also in loops. the particular problem occurs while solving Differential equation involving He's Homotopy purturbation method

exact_solution_error.mw

P1=(D1*ga+C1)/(1+ga) and P2= (D1-C1)/(1+ga), How to substitute in the solution of U_exact and Theta_exact

Please help me to solve

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? 

Questions are as follows:

Consider a g function, for example: g = 1 - (x_1 - 1)^2/9 - (x_2 - 1)^3/16;

Among them, x_1 and x_2 each conform to the normal distribution, and each has a mean mu_1 mu_2 and a variance sigma_1 sigma_2;

mu_1 and mu_2 both obey uniform distribution (-0.2, 0.2) respectively; sigma_1 and sigma_2 both obey uniform distribution (0.8, 1.2) respectively;

Set parameter theta = (theta_1, theta_2, theta_3, theta_4)^T = (mu_1, mu_2, sigma_1, sigma_2)^T;

It should be possible to obtain an analytical solution with only theta for the mean and variance of the g function, such as:

1. Ey = -(1/9)*theta[1]^2 + (2/9)*theta[1] + 137/144 - (1/16)*theta[2]^3 + (3/16)* theta[2]^2 - (3/16)*theta[2] - (3/16*(-1+theta[2]))*theta[4]^2 - (1/9)*theta[3 ]^2;
2. Vy = (1/20736)*(9*theta[2]^3 + 16*theta[1]^2 - 27*theta[2]^2 - 32*theta[1] + 27*theta[2] - 137)^2 + (15/256)*theta[4]^6 + (45/256*(theta[2]^2 - 2*theta[2] + 1))*theta[4]^4 + ( 1/768*(45*theta[2]^4 + 32*theta[1]^2*theta[2] - 180*theta[2]^3 - 32*theta[1]^2 - 64*theta[ 1]*theta[2] + 270*theta[2]^2 + 64*theta[1] - 436*theta[2] + 301))*theta[4]^2 + (1/27)*theta[ 3]^4 + (1/216)*theta[3]^2*(3*theta[2]^3 + 16*theta[1]^2 - 9*theta[2]^2 - 32*theta[ 1] + 9*theta[2] - 35) + (1/24)*theta[3]^2*(-1+theta[2])*theta[4]^2;

But I can't find the above analytical solution. The code I wrote in maple is as follows:

restart;

with(Statistics);

x[1] := RandomVariable(Normal(theta[1], theta[3]));

x[2] := RandomVariable(Normal(theta[2], theta[4]));

g := 1 - (x[1] - 1)^2/9 - (x[2] - 1)^3/16;

theta[1] := RandomVariable(Uniform(-0.2, 0.2));

theta[2] := RandomVariable(Uniform(-0.2, 0.2));

theta[3] := RandomVariable(Uniform(0.8, 1.2));

theta[4] := RandomVariable(Uniform(0.8, 1.2));

mean := Mean(g);

variance := Variance(g);

mean;

variance;

As a result, after clicking Run, the following problems occur:

Problem 1: The program takes a very long time to run

Problem 2: The program results did not meet expectations, because the results I expected were：

Ey = -(1/9)*theta[1]^2 + (2/9)*theta[1] + 137/144 - (1/16)*theta[2]^3 + (3/16)* theta[2]^2 - (3/16)*theta[2] - (3/16*(-1+theta[2]))*theta[4]^2 - (1/9)*theta[3 ]^2;

Vy = (1/20736)*(9*theta[2]^3 + 16*theta[1]^2 - 27*theta[2]^2 - 32*theta[1] + 27*theta[2] - 137)^2 + (15/256)*theta[4]^6 + (45/256*(theta[2]^2 - 2*theta[2] + 1))*theta[4]^4 + ( 1/768*(45*theta[2]^4 + 32*theta[1]^2*theta[2] - 180*theta[2]^3 - 32*theta[1]^2 - 64*theta[ 1]*theta[2] + 270*theta[2]^2 + 64*theta[1] - 436*theta[2] + 301))*theta[4]^2 + (1/27)*theta[ 3]^4 + (1/216)*theta[3]^2*(3*theta[2]^3 + 16*theta[1]^2 - 9*theta[2]^2 - 32*theta[ 1] + 9*theta[2] - 35) + (1/24)*theta[3]^2*(-1+theta[2])*theta[4]^2; 

so,i dont know where i am wrong ,how could i obtain the expected solution?

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];
 if leader=0 then selectremove(thickness=0,parms);end if;
[op(parms),thickness=3];
display(plottools:-line([1,2], [3,4]),op(parms));

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

Edit: uploaded Maple 3d plot.
 

Download Tetrahedron_Rat_Trig.mw

How to find all occurrences with Fibonacchi numbers?
100=89+8+2+1=89+5+3+1=55+34+8+2+1 etc...

fib := proc(n::nonnegint) option remember; if n <= 1 then n; else fib(n - 1) + fib(n - 2); end if; end proc;
zeck := proc(n::posint) local k, d; k := 2; while fib(k) <= n do k := k + 1; end do; d := n - fib(k - 1); if d = 0 then k - 1; else k - 1, zeck(d); end if; end proc;
zeck(100);
E := [fib(11), fib(6), fib(4)]; add(E[i], i = 1 .. nops(E));

Hi,

For optimal display, I would like to enlarge the size of numbers in the TextArea. Any ideas? Thank you.

S4ThalèsAnimation.mw

Hello

I have a list N with i elements, for example N:=[7,2,4] with i = 3. From another list L I know, that all the elements of N are also elements of L, but I don't know if they are in the same order. For example:

In L1=[2,6,5,7,3,2,9,4] the elements are in the same order, but they are not in L1=[2,1,4,2,6,7,3,9]. 

How to write a program that can say wether the elements are in the correct order or not?

Thanks for your help!

For the past days I observe that reply to posts stucks at the progess bar

(using a firefox browser). I am wondering whether that is only on my installation. Loading pages is not slow as reported here. I have a suspicion that this happens after having previewed a reply before submission. I observe also sometimes a yellow background of the preview and sometimes a blue background.

I try to submit now with blue backgound

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

Download Units_and_Integrals.mw

Hi,

I can't understand the error message generated during this animation. Any ideas? Thanks

TriagleSemblablesTest.mw

I want to have a 14 larger font instead of Times New Roman 12 for the whole worksheet or else a different font later. 
Can't make sense of how this is all organized in Maple 
You would say set a template , but ?

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!