## How to find a Perpendicular Vector...

I am looking for an elegant way in which to find a vector that is perpendicular to another vector.  The attached worksheet shows one method, but this can result in a divide by zero error.  I could write a procedure to detect and avoid the divide by zero error, but this feels like a sledgehammer to crack a nut :-)

Another method might be to rotate the vector by PI/2, but I'm not sure how to do this.

Any suggestions would be gratefully received!

Perpendicular_Vectors.mw

## How to make this code more efficient?...

Hi,
I need do generate a large number of matrices (always with the same dimensions) whose each column is a random sample of a different random variable.
I wrote a rather simple procedure to do that (see below a notional example). Let T and S the time and the memory size required for a single execution of this procedure, then its execution N times needs a time N*T and a size N*S.
If time is not a problem, the increase in memory size is extremely constraining.
How should I write this procedure in order that N executions of it use a memory of the order of S and not N*S?

## datatype = float[8])) error...

upload the mw file here faq.mw

Also i have a working for lopp and want to make a procedure.
Any suggestions will be helpful as well. Thanks.

## Re: Chain rule + how to refer to a previous result...

This is a given set of equations (from a classifier problem in deep learning):

I tried to replicate the expression in Maple, but it was unsuccessful.

Q_MaplePrime20200417.mw

Would you tell me how to make it work?

Then, please let me know how to refer to a previous result (equation number) in the current expression.

The last line above (and the attached Maple document) shows my attempt, It did not work.

Thank you/Be healthy!

## Error, invalid input: subs received Data, which is...

Hello,

How to solve this error? Thank you

Sistem := diff(E[1](t), t) = subs(E[1] = E[1](t), L[1] = L[1](t), P[1] = P[1](t), M[1] = M[1](t), E[2] = E[2](t), L[2] = L[2](t), P[2] = P[2](t), M[2] = M[2](t), Data, dE1), diff(L[1](t), t) = subs(E[1] = E[1](t), L[1] = L[1](t), P[1] = P[1](t), M[1] = M[1](t), E[2] = E[2](t), L[2] = L[2](t), P[2] = P[2](t), M[2] = M[2](t), Data, dL1), diff(P[1](t), t) = subs(E[1] = E[1](t), L[1] = L[1](t), P[1] = P[1](t), M[1] = M[1](t), E[2] = E[2](t), L[2] = L[2](t), P[2] = P[2](t), M[2] = M[2](t), Data, dP1), diff(M[1](t), t) = subs(E[1] = E[1](t), L[1] = L[1](t), P[1] = P[1](t), M[1] = M[1](t), E[2] = E[2](t), L[2] = L[2](t), P[2] = P[2](t), M[2] = M[2](t), Data, dM1), diff(E[2](t), t) = subs(E[1] = E[1](t), L[1] = L[1](t), P[1] = P[1](t), M[1] = M[1](t), E[2] = E[2](t), L[2] = L[2](t), P[2] = P[2](t), M[2] = M[2](t), Data, dE2), diff(L[2](t), t) = subs(E[1] = E[1](t), L[1] = L[1](t), P[1] = P[1](t), M[1] = M[1](t), E[2] = E[2](t), L[2] = L[2](t), P[2] = P[2](t), M[2] = M[2](t), Data, dL2), diff(P[2](t), t) = subs(E[1] = E[1](t), L[1] = L[1](t), P[1] = P[1](t), M[1] = M[1](t), E[2] = E[2](t), L[2] = L[2](t), P[2] = P[2](t), M[2] = M[2](t), Data, dP2), diff(M[2](t), t) = subs(E[1] = E[1](t), L[1] = L[1](t), P[1] = P[1](t), M[1] = M[1](t), E[2] = E[2](t), L[2] = L[2](t), P[2] = P[2](t), M[2] = M[2](t), Data, dM2);
Error, invalid input: subs received Data, which is not valid for its 9-th argument

## Direct Search Optimization...

Hi,

I am using Direct Search Optmization package for a procedure using Search command and everytime I run it it'll give me a different answer. same procedure, same code, when executed few times every time it generates a different answer. Can anyone help me with this ?

## How to prevent debug values displaying in the work...

When executing DEBUG within inline code (not within a procedure) the values displayed in successive debug windows (on clicking continue) are added to the end of my worksheet. How can the latter display be prevented?

## how to integrate arccos(x)*arcsin(x)?...

This Anti-derivative of  arccos(x)*arcsin(x), Maple  2020 cannot do that? It seems not difficult.

int(arccos(x)*arcsin(x),x)

In Mathematica, we can easily to get output :

2 x - Sqrt[1 - x^2] ArcSin[x] +  ArcCos[x] (Sqrt[1 - x^2] + x ArcSin[x])

## Startup Code reexecuted when pressing "Execute ent...

When pressing !!! (Execute entire worksheet) it seems to me that startup code is executed.

Is that correct, and if - why is that so?

## How to change coordinate?...

How can I transform the following differential equation from (x,t) to (X,T) coordinate, where, for example, X=x-alpha*t, T=beta*t (alpha and beta are constant)

diff(z, t)+(diff(R, x))*L+A*(diff(L, x))+diff(k, x, x)-(diff(k, t, t)) = 0

Thanks.

## 1D wave equation using d'Alembert's formula and an...

D(u(x,t),t,t)=c^2*D(u(x,t),x,x);

Where u(x,0)=f(x),D[2](u)(x,0)=g(x),u(0,t)=0=u(L,t),L=2

please do this as mentioned above

## Cant plot my procedure...

Dear all

I use Maple 2018 and have following problem:

I define following procedure and want to plot it. However Maple displays the coordinate system but does not plot anything nor gives and error message. Hope you can help.

Thanks

b:=proc(n)
local b,i:
for i from 0 to n do
if i=0 then
b[0]:=0:
elif i=1 then
b[1]:=1:
else
b[i]:=(b[i-1]+b[i-2])/2:
end if:
end do:

return b[n]

end proc:

plot(b,0..10)

## what happened to this question and answer?...

Why was the question and answer deleted for this?

https://www.mapleprimes.com/questions/229329-How-Can-We-Solve-Following-1D-Wave-Equation

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