## How do i correct "error, illegal use of an object ...

HHow do i correct "error, illegal use of an object as a name"

## Singular Matrix in system of 4 ODEs...

Hello everyone,

I am trying to solve a system of 4 ODEs that describe a physical system, however, I get the message:

Error, (in dsolve/numeric/bvp) matrix is singular

Any help is much appreciated. The initial conditions are such that to find solution in steady state, that means, v(0)=v(period) and so on with all variables.

## ERROR in dsolve numeric: unable to store '...' whe...

Hello everyone,

I want to solve a simple ODE numerically having a piecewise periodic function in the ODE.

The periodic piecewise function definition is taken from this  post.

When solving using "dsolve" numerical, I get this error:

Error, (in f) unable to store '100000*square_wave_periodic' when datatype=float[8]

restart;
d := .5;
fs := 100*10^3;
Vin := 10;
C := 10*10^(-6);
R := 10;
L := 10*10^(-6);

DEFINE PERIODIC FUNCTION
square_wave := proc (t) options operator, arrow; piecewise(0 <= t and t <= d/fs, Vin, d/fs < t and t < 1/fs, 0) end proc

square_wave_periodic := proc (t) options operator, arrow; square_wave(t-floor(t*fs)/fs) end proc

ode1 := L*(diff(i(t), t))+v(t) = square_wave_periodic
ode2 := C*(diff(v(t), t))+v(t)/R = i(t)
IC := v(0) = 0, i(0) = 0
sol := dsolve({IC, ode1, ode2}, {i(t), v(t)}, numeric)

LCRcircuit_transient_numerical.mw

Any help is much appreciated ! Thank you !

## contour plot at ...

I tryning to to plot 3d and then contour plot of the function N vs alpha

N_vs_alpha.mw

## NLPsolve non numeric result...

Hello everyone,

I am trying to solve a simple nonlinear 4 variable function with NLPsolve giving real values ranges for the variables but the NLPsolve gives "non numerical" result. Find attached the worksheet.CoreOptimization.mw

Am I doing something wrong?

Regards,

Cata

## how can solve the problem when it says root of?...

Hhow can i solve R it says here root of

Calculate.mws

## Kernel stop. ...

How do you stop Maple during this code execution:

proc()
x:
print(1);
goto(x);
end():

## Solve equation given a list of coefficients...

Hello everyone,

I am trying to solve an equation using the "solve(...)" function but the coefficients of the equation are changing.

I am using the coefficients as list but the "solve(...)" function gives error: "Error, (in assuming) when calling 'Engine:-Dispatch'. Received: 'badly formed input to solve: not fully algebraic'"

I am attaching the Maple document.

However, what I want to achieve, is the solution for each value in the list.

Here is an easy example of what I am saying:

a=3*x+k where k=[list of values], a=[another list of values].

I want to find "x" for each pair of values (a,k) in the list.

Thank you !

LCC Resonant Converter - Frequency Finder

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## how to compute symbolic Expressions ...

H all expert

first this Expression

ni := diff(Q(x, t), t)+a*Q*(x, t)*(diff(Q(x, t), x))+b*(diff(Q(x, t), t\$3))+d*(diff(Q(x, t), t\$5)) = 0

then I want to solve  diff(Q(x, t), t\$5)

diff(Q(x, t), t\$5) = solve(ni, diff(Q(x, t), t\$5))#eq2

p (x, t) :=H1(t)*Q(x*H2(t), H3(t)) #assumption

k := diff(p(x, t), t)+a*p(x, t)*(diff(p(x, t), x))+diff(p(x, t), t\$3)+d*(diff(p(x, t), t\$5))+c*p(x, t) #eq3

r := subs(diff(Q(x, t), t\$5), k) #subs eq2 in eq3

i recived error

SUBS1.mw

## How to produce a graph of a numbers sequence...

Hi,

I have a code (see below) for the following number sequence and want to produce a graph as well as the numerical data, please advise how to do it.

Sequence definition: Lexicographicaly least sequence of nonnegative integers commencing 1,3,5,7 such that any four  consecutive terms are mutually coprime.

The code I have so far is:

ina := proc (n) false end :

a := proc (n) option remember; local k;

if n < 5 then k := 2*n-1

else for k from 2 while ina(k) or igcd(k, a(n-1)) <> 1 or igcd(k, a(n-2)) <> 1 or igcd(k, a(n-3)) <> 1

do  od

fi; ina(k) := true; k

end proc;

seq(a(n), n = 1 .. 100);
1, 3, 5, 7, 2, 9, 11, 13, 4, 15, 17, 19, 8, 21, 23, 25, 16, 27,

29, 31, 10, 33, 37, 41, 14, 39, 43, 47, 20, 49, 51, 53, 22, 35,

57, 59, 26, 55, 61, 63, 32, 65, 67, 69, 28, 71, 73, 45, 34, 77,

79, 75, 38, 83, 89, 81, 40, 91, 97, 87, 44, 85, 101, 93, 46,

95, 103, 99, 52, 107, 109, 105, 58, 113, 121, 111, 50, 119,

127, 117, 62, 115, 131, 123, 56, 125, 137, 129, 64, 133, 139,

135, 68, 143, 149, 141, 70, 151, 157, 153

I have tried listplot but for some reason cant get the correct format

Hope you can help

Best regards

David.

## How to solve auxiliary equation to find the famili...

Hi, I'm trying to solve auxilary equation to find its familes but I don't know what I'm doing wrong as I'm using following code:

famtemp := (diff(z(xi), xi))^2-a*z(xi)^2-b*z(xi)^3-c*z(xi)^4;

fam1 := simplify(`assuming`([dsolve(famtemp)], [b::real, a::real, c::real, -4*a*c+b^2 > 0, a > 0]))

I want to get the following family:

fam1 := 2*a*sech(sqrt(a)*xi)/(sqrt(-4*a*c+b^2)-b*sech(sqrt(a)*xi));

I hope someone will help me to solve it.

Thanks

## Maple linear solvers....

Given  3000 linear equations in 3000 unknowns, with coefficients in a field of rationals with one algebraic number extension, which Maple solver would be fastest in solving the system?

## get term from table...

have table like table(symmetric, [() = x]) from other code not mine, strange syntax

how to extract x from table thanks

## How to pass in temporary values to parameters of a...

I have an array with a list of parameters. Suppose there are three parameters, t1, t2 and t3. I like to evaulate the array for different values of the parameters. I can do it manually by a command such as

eval(array, {t1=1, t2=5, t3=10})

What is a more systematic approach and how can it be done? Suppose I do not know the number of paramters in advance and the number of parameters could possible be large. Once I know the number of parameters, I would like to map a list of values to the parameters.