## 68 Reputation

14 years, 246 days

## How to force half angle formula...

Maple

Hello,

I have a two expressions...

on in terms of

sin(1/2*B*L) and sinh(1/2*B*L)

and another in terms of

sin(B*L) and sinh(B*L)

I'd like to use a half angle formula on the first to get it in terms of "B*L", then make a substitution into the second...I can't seem to figure out how to make maple do a 1/2 angle expansion....

any suggestions?

## dsolve to get eigenvalues...

Maple

When I execute the code below, dsolve returns the trivial solution. If I were to apply the BCs by hand I'd conclude that there is a set of eigenvalues associated with the ODE. Is there a way to have Maple produce the eigenvalue equation automatically, or would you typically apply the BCs by hand to find it?

Y_diffEq:=diff(y(x),x\$4)-beta^4*y(x)=0;
Y_BCs:=y(0)=0, (D@@2)(y)(0)=0, y(L)=0, (D@@2)(y)(L)=0;
dsolve({Y_diffEq,Y_BCs},y(x));

PS

Is there another way to specify the derivative BC?

Thank you

## Pass string array to external Fortran fu...

Maple

Hello,

I would like to pass a string array to an external FORTRAN function, can this be done without generating wrapper code...I don't have a FORTRAN compiler...

The Fortran datatype is

character*255 hf(20)

In FORTRAN I would pass say "hf(1)='nitrogen.fld'", but I'm not sure what datatype to use in the maple define_external function or how to pass the data in?

## Problem w/ algsubs...

Maple

Hello,

I'm getting an error from algsubs that I don't understand...

This works fine....

EqD16a := (-w[j]+w[c]+3*w[c]*alpha)*(-w[j]+w)^2/(alpha*(-w[j]+w[c])^3);

EqD16b:=algsubs(w=beta*w[j],EqD16a);

This fails...

EqD15a := (-w[j]+w)*(-2*w[c]*alpha+2*w[c]-2*w+3*w*alpha-w[j]*alpha)/(alpha*(-w[j]+w[c])^2);
EqD15b:=algsubs(w=beta*w[j],EqD15a);
Error, (in collect/series) invalid expression for series

I don't understand why the second fails?

## Using define_external w/ Fortran Array...

Maple

Hello,

I'm try to access some external Fortran routines within maple. I have a Fortran datatype of

character*255 hf(20)

This is an input parameter, and I believe this will map into a maple Array object, but I'm not sure of the datatype. The help says that the datatype can only be "hardware datatypes" so I take to mean it would have to be of type integer[4]...when I do this I get the error below.

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