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Question: Applying fsolve to unknowns of type x(0)

Question:Applying fsolve to unknowns of type x(0)

Rouben Rostamian 7938 Maple 2020
solve fsolve
September 17 2020
1
 
> 

restart;
> 

kernelopts(version);

`Maple 2020.1, X86 64 LINUX, Jul 30 2020, Build ID 1482634`

This one works as expected:

> 

solve({x + y = 5, x - y = 3});

{x = 4, y = 1}

This one fails:

> 

solve({x(0) + y(0) = 5, x(0) - y(0) = 3});

That shouldn't fail.  According to ?solve,details, under the Description

heading, it says that the unknown may be a name or a function.  Note that

> 

type(x(0), function);

true

so there seems to be a contradiction.  Nevertheless, there is a workaround:

> 

solve({x(0) + y(0) = 5, x(0) - y(0) = 3}, {x(0), y(0)});

{x(0) = 4, y(0) = 1}

> 

 

Now try with fsolve().  This one works as expected:

> 

fsolve({x + y = 5, x - y = 3});

{x = 4., y = 1.}

This one fails:

> 

fsolve({x(0) + y(0) = 5, x(0) - y(0) = 3});

But the previous workaround does not help:

> 

fsolve({x(0) + y(0) = 5, x(0) - y(0) = 3}, {x(0), y(0)});

I can temporarily rename the variables to plain symbols, or perhaps

freeze/thaw them.  But is there a simpler workaround?

 

 

Download fsolve-problem.mw

 
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