## How do I solve an ode numerically and then plot th...

Hello,

I'm new at Maple, so I'm still trying to figure out basic stuff. I have solved an ode with t as independent variable and x as dependent one and I have used plots[odeplot] to plot x over t, but I also need to plot t over x. Any ideas how I can do that? Here's my code:

ode := diff(x(t), t) = 16250.25391*(1 - (487*x(t))/168 + 4*Pi*x(t)^(3/2) + (274229*x(t)^2)/72576 - (254*Pi*x(t)^(5/2))/21 + (119.6109573 - (856*ln(16*x(t)))/105)*x(t)^3 + (30295*Pi*x(t)^(7/2))/1728 + (7.617741607 - 23.53000000*ln(x(t)))*x(t)^4 + (535.2001594 - 102.446*ln(x(t)))*x(t)^(9/2) + (413.8828821 + 323.5521650*ln(x(t)))*x(t)^5 + (1533.899179 - 390.2690000*ln(x(t)))*x(t)^(11/2) + (2082.250556 + 423.6762500*ln(x(t)) + 33.2307*ln(x(t)^2))*x(t)^6)*x(t)^5

ics := x(0) = xlow

solx := dsolve({ics, ode}, numeric, range = 0 .. tfin)

plots[odeplot](solx, 0 .. tfin)

## fractional order differential equation ...

Hi

I have the following fractional  system of differential equation. How to plot it for alpha=0.5, beta=0.5?

eq1:=diff(y1(t),t\$alpha)=0.04-(0.09*y1(t)*y2(t))-(0.00250*y1(t)*y2(t))/((0.03500+y2(t)))-0.04*y1(t);

eq2:=diff(y2(t),t\$beta)=(0.09*y1(t)*y2(t))+(0.00250*y1(t)*y2(t))/((0.035+y2(t)))-(0.02+0.04)*y2(t);

## How to use printf with units or an alternative?...

Hello

I have a funtion defined as

`a := diff(u*ln(m__o/(-q*t + m__o)) - g*t, t)`

where m_0, q, g, and u are constants with dimensions. T is the variable and has dimensions as well. I need to print out columns of this function and other similar functions, v and h, in 4 seconds intervals of t. So what I have is this:

```for i from -4 by 4 to 80 do
if i = -4 then printf("%12s %18s %15s %15s \n", "time", "acceleration", "velocity", "altitude"); else printf("%10d %c %10.2f  %s %10.2f  %s %10.2f  %s \n", i, "s", eval(a, t = i), "ft/s^2", eval(v, t = i), "ft/s", eval(h, t = i), "mi"); end if;
end do```

this works perfectly fine until I assign units to the constants and t. Then I get the error: Error, (in fprintf) number expected for floating point format.

Then I also need to plot a v and h against t. Seems like plot doesn't work either with units.

So what do i do?

Thanks

## Combining arrays...

Hello. I have the equations written into the arrays. I want to combine them into a common system and solve it. I gave a simple example of what I need. How do I perform this operation?

 >
 >
 (1)
 >
 (2)
 >
 >

## how to place the calculated elements in a matrix ?...

restart; with(Student[LinearAlgebra]); A := Matrix([[2, 3, -4], [0, -4, 2], [1, -1, 5]]); for i to 3 do for j to 3 do print((-1)^(i+j)*Minor(A, i, j)) end do end do; How to code to get that is egal to Adjoint(A)? Thank you.

## Maple 2020 loads in eternity after 1 action...

Hi,

Whenever I open Maple 2020 and type one single letter or number (doesn't matter) Maple 2020 will "freeze" and load forever (i have had it open for a long time, just watching that f**king blue circle spin...

I have tried reinstalling, repairing, running as admin, and changing the compatibility mode, still, nothing works:(

I run Maple 2020 as a Student with WithGym

Pc specs:

Intel i5-10300h 2.6 ghz

Geforce 1660 ti 6gb

Windows 10 x64

## RE: How to check if two expressions are the same...

Hello there,

Would you tell me how to check if the two expressions presented below are the same?

My simple attempt (at the end of the worksheet below) failed.

 > restart;
 > subexpx := Ls*cos(omega*t + phi__l + theta)*omega + sin(omega*t + phi__l + theta)*Rs;
 (1)
 > subexpx2 := sqrt((omega*Ls)^2+Rs^2)*sin(omega*t + phi__l + theta + arctan(omega*Ls/Rs));
 (2)
 > is(subexpx - subexpx2 = 0) assuming omega::positive, Ls::positive, Rs::positive;
 (3)
 >
 >

Thank you,

Hi
I want to say maple convert this radicals to a single radical expr.

convert to :

thank u .

## Matrix multiplication...

Hi,

I don't speak well in english but I 'll try

I can't print a matrix multiplication without maplke simplify it

i want

A*b=x

so

|1 2 3|     |x|        |1|

|4 5 6|  * |y|    =   |2|

|7 8 9|     |z|        |3|

but maple simplify A*x

so i have something like

|1x 2y 3z|            |1|

|4x 5y 6z|       =   |2|

|7x 8y 9z|            |3|

Thank a lot.

## why dsolve gives numeric exception: division by ze...

In this ODE

dsolve gives

When A=3 but  not when A=1 or A=2

```restart;
ode:=(1+y(x))*diff(y(x),x\$2)-A*diff(y(x),x)^2=x;
A:=1;
dsolve(ode):
A:=2;
dsolve(ode):
A:=3;
dsolve(ode):
```

The problem is not with the particular solution. Maple can find that

`DEtools:-particularsol(ode,y(x))`

And it can solve the homogeneous ODE for any A:

```restart;
ode:=(1+y(x))*diff(y(x),x\$2)-A*diff(y(x),x)^2=0;
A:=1;
dsolve(ode):
A:=2;
dsolve(ode):
A:=3;
dsolve(ode);
```

Is this a known issue and why it happens on some values?

Maple 2020.1 and Physics 861 on windows 10

## problem with sum ...

Hi,

i try to calculate the sum of  Eff elements , but i receive this message?

SumQuestion.mw

## How to Remove Column from dataframe?...

Hi,

I try to remove first column from my df variable, but the command Remove(df,1) don't work. Ideas ?

Thanks

SérieTabulateStat.mw

## How can I integral from dsolve answer?...

hello

I am beginner in maple.

I have a differential equation system with 17 equations. I used dsolve() function and my code worked.

Now, I want to integral from the dsolve answer.but I dont know how?

## How to generate random elements of matrix ...

Hi, how to generate a matrix ( 6X2) with different random integers  ( between 10 and 20) in the first column and others random integers ( between 50 and 100) in the second column ?

Thanks

SérieTabulateStat.mw