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Honigmelone

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Eval Physics[diff]...

Honigmelone 102 Maple
eval physics diff
April 11 2016
1 1

Hey all,

I want to symbolically differentiate a function and recalculate the result later. Here is what I have tried so far:


> 

restart;
> 

myexp:=dfdb+sthlong

dfdb+sthlong

 (1)
> 

b:=<b1(t),b2(t)>;

b := Vector(2, {(1) = b1(t), (2) = b2(t)})

 (2)
> 

dfdb:=Physics[diff]~(f(b),b)

dfdb := Vector(2, {(1) = (D(f))(Vector(2, {(1) = b1(t), (2) = b2(t)})), (2) = (D(f))(Vector(2, {(1) = b1(t), (2) = b2(t)}))})

 (3)
> 

f:=b->b(1)^2+b(2)

proc (b) options operator, arrow; b(1)^2+b(2) end proc

 (4)
> 

eval(myexp);  #actual result
> 

 

> 

 

sthlong+(Vector(2, {(1) = (D(f))(Vector(2, {(1) = b1(t), (2) = b2(t)})), (2) = (D(f))(Vector(2, {(1) = b1(t), (2) = b2(t)}))}))

 (5)
> 

dfdb:=Physics[diff]~(f(b),b):

> 

eval(myexp); #expected result

sthlong+(Vector(2, {(1) = 2*b1(t), (2) = 1}))

 (6)
> 

 


Download physics_diff.mw

I wonder if this is even possible, or if I missunderstand something. Can you please help me?

 

Thanks

 

Honigmelone

How to simplify this expression?...

Honigmelone 102 Maple
simplify substitution abs
March 03 2016
3 9

Hey,

is there a way to substitute funktion combinations when they have the same arguments? I want to substitute abs(exp)*abs(1,exp) with exp. Algsubs works as long as I know the excat expressions. However, I want to do this substitution for any exp. Simplify doen't work here ether.

I also tried to write my own simplification rule with no success:

> 

restart:
> 

f:=abs(a)*abs(1,a);
> 

 

abs(a)*abs(1, a)

 (1)
> 

siderel:={abs(x)*abs(1,x)=x};

{abs(x)*abs(1, x) = x}

 (2)
> 

simplify(f,siderel);    #expected result: a

abs(a)*abs(1, a)

 (3)
> 

 

> 

 

> 

 

 

Download simplify_abs.mw

 

Thanks in advance!

Assigning vector of symbols...

Honigmelone 102 Maple
assign vector symbol
March 02 2016
1 3

Hey,


I want to assign a value to a symbol stored in a vector. I know the position of the symbol in the vector. Is there an easy way to do this?

Here to illsutrate my problem:

> 

restart:
> 

vec:=<a,b,c>:
> 

vec(1):=1;    # expected result: a:=1

vec := Vector(3, {(1) = 1, (2) = b, (3) = c})

 (1)
> 

a;            # expected result: 1

a

 (2)
> 

 

 

Download point_to_element.mw

 

 

Possible Bug in Maple ...

Honigmelone 102 Maple 18
alias assume
February 26 2016
0 7

Hey,

I think I found a bug concerning the useage of assume and alias:

> 

restart:
> 

alias(a=a(t),b=b(t));

a, b

 (1)
> 

assume(a(t),real);
> 

getassumptions(a(t));

{((a(t))(t))::real}

 (2)
> 

assume(b(t),real);
> 

getassumptions(a(t));

{((b(t))(t))::real}

 (3)
> 

getassumptions(b(t));

{((b(t))(t))::real}

 (4)
> 

 

> 

 

> 

 

Commenting out the alias command produces correct results. I am on linux with build 922027.

alias_bug.mw

Is there an analog of MATLAB tilde?...

Honigmelone 102 Maple
matlab tilde
February 24 2016
1 2

Hey,

I wonder if there is an operator to skip inputs and outputs of functions. Consider this example:

The output would be:

However my system is much bigger and I only need the second output of the command and I dont want to waste memory on the first.

In Matlab I would write

~,ans := GenerateMatrix(...)Is there a similar shortcut availible in Maple?

 

Thanks in advance!

 

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