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These are questions asked by nm

ODESteps gives division by zero for basi...

nm 11643 Maple 2024
ode differential-equations exception
May 31 2024
2 0

Any workaround or why ODESteps gives this internal Maple error?  Is this known limitation of ODESteps?

ps. reported also to Maplesoft just in case.

17128

> 

interface(version);

`Standard Worksheet Interface, Maple 2024.0, Windows 10, March 01 2024 Build ID 1794891`

> 

Physics:-Version();

`The "Physics Updates" version in the MapleCloud is 1750 and is the same as the version installed in this computer, created 2024, May 31, 10:47 hours Pacific Time.`

> 

restart;

20456

> 

ode:=diff(y(x), x) - 2*y(x) = 2*sqrt(y(x));
DEtools:-odeadvisor(ode);
 

diff(y(x), x)-2*y(x) = 2*y(x)^(1/2)

[_quadrature]

> 

ic:=y(0) = 1;
Student:-ODEs:-ODESteps([ode,ic]);

y(0) = 1

Error, (in ln) numeric exception: division by zero

> 

restart;

20456

> 

ode:=diff(y(x), x) - 2*y(x) = 2*sqrt(y(x));
ic:=y(0) = 1;
dsolve([ode,ic]);

diff(y(x), x)-2*y(x) = 2*y(x)^(1/2)

y(0) = 1

y(x) = 4*exp(2*x)-4*exp(x)+1

 

 

Download bug_in_odesteps_divide_by_zero_may_31_2024.mw

why Maple gives extra solutions to this ...

nm 11643 Maple 2024
ode dsolve differential-equations
May 24 2024
1 0

Given the ode   y''(x)*y'(x)=0, clearly it has solutions for y''=0 and y'=0.

These are y=c1+x*c2 and y=c1. But Maple gives 3 solutions

12592

> 

interface(version);

`Standard Worksheet Interface, Maple 2024.0, Windows 10, March 01 2024 Build ID 1794891`

> 

ode:=diff(y(x),x$2)*diff(y(x),x)=0;

(diff(diff(y(x), x), x))*(diff(y(x), x)) = 0

> 

dsolve(ode)

y(x) = c__1, y(x) = -c__1*x+c__2, y(x) = c__1*x+c__2

> 

dsolve(diff(y(x),x$2)=0)

y(x) = c__1*x+c__2

> 

dsolve(diff(y(x),x)=0)

y(x) = c__1

 

 

Download why_3_solutions_may_24_2024.mw

Where did the third solution come from? The 3 solutions are correct ofcourse, but why 3? There should only be two. 

FYI, I am using 

Physics:-Version()

The "Physics Updates" version in the MapleCloud is 1746. The 

   version installed in this computer is 1745 created 2024, May 

I have to check earlier Maple versions to see if same thing happens there.

why ODESteps(ode) unable to solve this f...

nm 11643
step-by-step differential-equations student
May 24 2024
4 4

This ode can be solved by just looking at it

ode:=(x+y(x))*diff(y(x),x)=0;

We see the solution is y=-x and y=c__1 because either (x+y)=0 or y'=0

But for some reason ODESteps(ode) says it cannot compute integral.

Any idea why?


 

26348

> 

interface(version);

`Standard Worksheet Interface, Maple 2024.0, Windows 10, March 01 2024 Build ID 1794891`

> 

ode:=(x+y(x))*diff(y(x),x)=0;
Student:-ODEs:-ODESteps(ode);

ode := (x+y(x))*(diff(y(x), x)) = 0

"[[,,"Let's solve"],[,,(x+y(x)) ((ⅆ)/(ⅆx) y(x))=0],["•",,"Highest derivative means the order of the ODE is" 1],[,,(ⅆ)/(ⅆx) y(x)],["•",,"Integrate both sides with respect to" x],[,,∫(x+y(x)) ((ⅆ)/(ⅆx) y(x)) ⅆx=∫0 ⅆx+`c__1`],["•",,"Cannot compute integral"],[,,∫(x+y(x)) ((ⅆ)/(ⅆx) y(x)) ⅆx=`c__1`]]"

> 

 


 

Download odestep_quadrature_unable_to_solve_maple_2024.mw

update:

Here is another simpler example that also confused it
 

26348

> 

interface(version);

`Standard Worksheet Interface, Maple 2024.0, Windows 10, March 01 2024 Build ID 1794891`

> 

ode:=x*diff(y(x),x)=0;
Student:-ODEs:-ODESteps(ode);

ode := x*(diff(y(x), x)) = 0

"[[,,"Let's solve"],[,,x ((ⅆ)/(ⅆx) y(x))=0],["•",,"Highest derivative means the order of the ODE is" 1],[,,(ⅆ)/(ⅆx) y(x)],["•",,"Integrate both sides with respect to" x],[,,∫x ((ⅆ)/(ⅆx) y(x)) ⅆx=∫0 ⅆx+`c__1`],["•",,"Cannot compute integral"],[,,∫x ((ⅆ)/(ⅆx) y(x)) ⅆx=`c__1`]]"

> 

 

> 

 


 

Download odestep_quadrature_unable_to_solve_v2_maple_2024.mw

update

Here is another one which it gets wrong. 
 

26348

> 

interface(version);

`Standard Worksheet Interface, Maple 2024.0, Windows 10, March 01 2024 Build ID 1794891`

> 

ode:=y(x)*diff(y(x),x)=0;
Student:-ODEs:-ODESteps(ode);

ode := y(x)*(diff(y(x), x)) = 0

"[[,,"Let's solve"],[,,y(x) ((ⅆ)/(ⅆx) y(x))=0],["•",,"Highest derivative means the order of the ODE is" 1],[,,(ⅆ)/(ⅆx) y(x)],["•",,"Integrate both sides with respect to" x],[,,∫y(x) ((ⅆ)/(ⅆx) y(x)) ⅆx=∫0 ⅆx+`c__1`],["•",,"Evaluate integral"],[,,((y(x))^2)/2=`c__1`],["•",,"Solve for" y(x)],[,,{y(x)=sqrt(2) sqrt(`c__1`),y(x)=-sqrt(2) sqrt(`c__1`)}]]"

> 

dsolve(ode);

y(x) = 0, y(x) = -c__1

> 

 


The correct solution is given by dsolve, which is y=0 and y=constant (I do not know why dsolve put minus sign in front of the constant, but it is still correct).

Download odestep_quadrature_unable_to_solve_v3_maple_2024.mw

 

 

Maple gives solutions may have been lost...

nm 11643 Maple 2024
solve
May 22 2024
0 5

I can't understand this behavior. Any idea why it happens?

Solve is able to solve equation   f(y)=x+A for y, but can't solve   f(y)=x for y.

This is unexpected for me. I do not see why it can solve it when RHS is x+A but not when RHS is just x.


 

21040

> 

interface(version);

`Standard Worksheet Interface, Maple 2024.0, Windows 10, March 01 2024 Build ID 1794891`

> 

Physics:-Version();

`The "Physics Updates" version in the MapleCloud is 1745. The version installed in this computer is 1744 created 2024, April 17, 19:33 hours Pacific Time, found in the directory C:\Users\Owner\maple\toolbox\2024\Physics Updates\lib\`

> 

restart;

21040

> 

sol:=int(1/sqrt(sin(y)),y);
solve(sol=x,y)

(sin(y)+1)^(1/2)*(-2*sin(y)+2)^(1/2)*(-sin(y))^(1/2)*EllipticF((sin(y)+1)^(1/2), (1/2)*2^(1/2))/(cos(y)*sin(y)^(1/2))

Warning, solutions may have been lost

> 

sol:=int(1/sqrt(sin(y)),y);
solve(sol=x+b,y):
{%}; #to eliminate duplicates

(sin(y)+1)^(1/2)*(-2*sin(y)+2)^(1/2)*(-sin(y))^(1/2)*EllipticF((sin(y)+1)^(1/2), (1/2)*2^(1/2))/(cos(y)*sin(y)^(1/2))

{arctan(JacobiSN(((1/2)*I)*2^(1/2)*(x+b), (1/2)*2^(1/2))^2-1, -(1/2)*JacobiSN(((1/2)*I)*2^(1/2)*(x+b), (1/2)*2^(1/2))*(4-2*JacobiSN(((1/2)*I)*2^(1/2)*(x+b), (1/2)*2^(1/2))^2)^(1/2)*2^(1/2)), arctan(JacobiSN(((1/2)*I)*2^(1/2)*(x+b), (1/2)*2^(1/2))^2-1, (1/2)*JacobiSN(((1/2)*I)*2^(1/2)*(x+b), (1/2)*2^(1/2))*(4-2*JacobiSN(((1/2)*I)*2^(1/2)*(x+b), (1/2)*2^(1/2))^2)^(1/2)*2^(1/2))}

> 

 


I can trick it to solve  f(y)=x for y  by asking it to solve f(y)=x+A for y and then set A=0 in the solution. But one should not have to do this. Is this a bug or Am I missing something?

Download why_solve_when_adding_term_only_may_22_2024.mw

ODEs:-ODESteps gives error on first orde...

nm 11643 Maple 2024
ode differential-equations odesteps
May 10 2024
2 5

Why Maple gives this error on solving first order linear ode using ODESteps? 

26004

> 

interface(version);

`Standard Worksheet Interface, Maple 2024.0, Windows 10, March 01 2024 Build ID 1794891`

> 

Physics:-Version();

`The "Physics Updates" version in the MapleCloud is 1744 and is the same as the version installed in this computer, created 2024, April 17, 19:33 hours Pacific Time.`

> 

ode:=diff(y(x),x)+x*y(x)=1;
ic:=y(0)=0;
dsolve([ode,ic]);

diff(y(x), x)+x*y(x) = 1

y(0) = 0

y(x) = -((1/2)*I)*exp(-(1/2)*x^2)*Pi^(1/2)*2^(1/2)*erf(((1/2)*I)*2^(1/2)*x)

> 

Student:-ODEs:-ODESteps([ode,ic])

Error, (in Student:-ODEs:-OdeSolveOrder1) invalid input: too many and/or wrong type of arguments passed to solve; first unused argument is _C1

 

 

Download odesteps_fail_may_10_2024.mw

ps. also reported to Maplesoft customer support.

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