## Problem using units with differential equation pro...

Hi

I am doing a differential equation problem and decided to add units. However, when using dsolve i get the error:

"Error, (in dsolve) the units s and 1 have incompatible dimensions"

Can some of you experts see where i am wrong?

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## Multiply contents of vector to get expected value...

Hi

This worksheet by Jason Schattman, I cant work out how he gets vector r, the expected value (in bold). I did ask him. Anybody shed any light?

I thought EV was calculated by averaging each stocks yearly returns. EV for Q[1] is (0.08-0.2+.05)/3   (<> 0.05)

Obviously i'm going to get a different r to him, but out of interest what maple commands do i need to convert Q into r using my method for EV?

portfoliooptimizati.mw

## How can I find the angles alpha, beta, epsilon to ...

I want to draw circle passing thought three points S, A, B on the sphere by using tikz-3dplot-circleofsphere, its document at here https://github.com/matthias-wolff/tikz-3dplot-circleofsphere/blob/master/tikz-3dplot-circleofsphere.pdf The command to draw is
\tdplotCsDrawCircle[style]{r}{alpha}{beta}{epsilon}

With Maple, I can find the coordinates of center and radius of circle. I tried

restart;
with(geom3d):
a := 3:
b := 4:
h := 5:
point(A, 0, 0, 0):
point(B, a, 0, 0):
point(C, a, b, 0):
point(DD, 0, b, 0):
point(S, 0, 0, h):
sphere(s, [A, B, C, S], 'centername' = m); detail(s); plane(p, [S, A, B], [x, y, z]); coordinates(projection(H, m, p));
R := distance(H, S)

But, I can't to find the angles alpha, beta, epsilon to draw this circle. How can I find  the angles alpha, beta, epsilon?

## Including regular discontinuities in a system of O...

Hi

I am woking on a pharmo model for a freind, and it includes a variable called depot that needs to jump up by 150 every 24 hours.
currently I have written it as:

clearly thats wrong though, as the +150 s don't make it jump up by 150 because of the small step size.

(at t=0, it adds 150*a small step size, at 24 it looks like it adds 150* a vastly smaller step size, what I want would be much closer to a series of pulses each decaying to almost 0 and then getting boosted to just over 150)

My intuition is that i need to use the dirac delta function but in such a way that its integral adds 150 instantaneoulsy every 24 hours. I have no idea how to do that!

Lindas_signal_transduction_model_2.mw

[Edit:
I've just realised that this ode has an obvious solution, so you can trivially make a function that adds 150 every 24 hours and exponentially decays in between.  However there are other models that hopefully i'll being doing similar work on, that don't have nice solutions]

## How to adjust width and height of animated gif fil...

Hello

When i export an animation as a gif the dimensions are (by default it seems) 400x400 pixels (w x h).

But my slide show requires a dimension of 1920 x 1080 pixels.

How to I tell maple to export a gif of predefined dimensions?

I can manually adjust the dimensions of the animation by grabbing a corner and pulling it right and down and then export it, but its hit and miss.

Here is an example animation written by Kitonum

restart;
with(DEtools):
rho := 0.1:
w0 := 2:
sys := a->[diff(x(t),t) = y(t),diff(y(t),t) = -2*rho*y(t) - w0^2*(x(t)+a)];
P:=a->DEplot(sys(a), [x(t),y(t)], t = 0 .. 20-2*a, x=-2..2, y=-1.9..1.7, [[x(0) = cos(a)-a, y(0) = sin(a)]], scene = [x(t),y(t)], linecolor=blue, numpoints=1000):
plots:-animate(plots:-display,['P'(a), size=[600,300]], a=-0.7..1.4, frames=90);

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## How to ensure that dsolve works ...

Hi i was trying to numerically integrate my freinds model with dsolve, and i am sure that I have put all the right components in the command as described in the help page, but it doesn't work. (Here is a worksheet with the model Lindas_signal_transduction_model.mw )

What is the problem with the way I have called the function?
Does anyone have a mental checklist that they use for dsolve commands? because I often struggle with making them work.

## problem using DEtools [rifsimp]...

Hello all
I'm working on calculating the conservation laws for a Gardner equation
During calculation interface problem using []

The problem is that this function only works for integer exponents

Is there another way to overcome this

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## Encrypt Procedure Question...

Hello

I found this example in the Help.

I'm wanting to export the encrypted file (the gibberish between local and end proc) to friend running another M2018, and want it to run.

I would need to rerieve "abc.mla" repository that we saved it in. But I cant find it. and if i did send it, he would be able to decrypt it surely?

Encrypt_Proc.mw

Hi,
I had written some help pages in Maple 18 that I just migrate in Maple 2018.
This seems correct except one single point: when I try ot access them from the help menu, their names are preceeded by a  "WS" label and, when I click on it, the help page appears in a new window of my Maple's session, not in the help window.
I guess "WS" means "WorkSheet" ?
How can I force the halp page of "my" function to appear in the main help page window?

(hope I was clear enough)

## How to do "simple" vector calculation (with exampl...

 I want to calculate the voltage between phase 1 and phase N in an electrical circuit:   The vectorial formula is:   Voltage drops are calculated with the current multiplied with the resistance: ΔU =   i   This is a real example with realistic values and angles. Note that i have two different vectors with the same index. This is on purpose and the vector is different. This is because the first vector is before the resistance in the wire and the one i want to find, is after the resistance in the wire (the red one).:   The negative angles is because i am using my reference which is in 0°. And are the vector to the right of my reference is the angle negative, and is it on the left of my reference is the angle negative. I dont want to explain the vectorial diagram, because i think it will do more confusion than explaining.     My question is, if the formula above is possible to solve in maple?     The result is calculated on my CAS-calulator:

The example in Maple:

## Solving two coupled PDEs which have complex pote...

I am having problems with the attached worksheet, in which I am attempting to solve a couple pair of PDEs, particularly in defining initial and boundary conditions.  See MapleExample1c.mw

Can anyone help?

Melvin

## What does VectorCalculus:-Curvature represent?...

Hi,

I'm surprised by the result of the procedure VectorCalculus:-Curvature which is always a positive scalar quantity:
For instance
c := VectorCalculus:-Curvature(<x, sin(x)>, x):
plot(c, x=0..2*Pi)
# c >=0 for all x in [0, 2*Pi]

In the help pages it's written that the (signed) curvature for a function y(x) is y''/(1+y' 2)(3/2).

y := sin(x):
c := diff(y, x\$2) / (1+diff(y,x)^2)^(3/2):
plot(c,  x=0..2*Pi)
# c < 0 if x in (0, Pi)  and  c > 0 if x in (Pi, 2*Pi)

## How to calculate the derivative of modified Bessel...

Hello,

How to calculate the derivative of modified Bessel fucntion of the first kind and order \alpha, such that \alpha>-1/2?

I need to calculate de general term of the derivative of modified Bessel function of the first kind and order \alpha.

Best regards