nm

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13 years, 88 days

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These are questions asked by nm

 

Not that I care about the virtual rating numbers here, but I am wondering why would one suddenly lose 15 point after posting a problem they found in Maple? Is this typical?

https://www.mapleprimes.com/questions/229443-Why-These-ODEs-Hang-Or-Return-Unsolved

3 hrs ago, I was 3001  and when I came to check on the status if any, now it says 2986.

Just wondering why, that is all. Again, this really does not bother me at all as I do not care about these virtual cloud credit points, and I only post here on occasions and when I found some problem. I just like to know why this happened just now, that is all. 

 

 

 

 

 

When I tried these ODE's in Maple 2019, and Maple 2018, they are worked (i.e. gave solutions). Now these ODE's either hang in 2020 or return unsolved. What could have caused this? On Maple 2020, under windows 10:

restart;
ode:=(x^2-1)*diff(y(x),x)^2-y(x)^2+1=0:
dsolve(ode); #hangs

restart;
ode:=(2*x^2+1)*diff(y(x),x)^2+(y(x)^2+2*x*y(x)+x^2+2)*diff(y(x),x)+2*y(x)^2+1=0:
dsolve(ode); # return unsolved

restart;
ode:=x*y(x)^2*diff(y(x),x)^3-y(x)^3*diff(y(x),x)^2+x*(x^2+1)*diff(y(x),x)-x^2*y(x):
dsolve(ode); # return unsolved

restart;
ode:=(diff(y(x),x) = (-y(x)^2+4*a*x)^3/(-y(x)^2+4*a*x-1)/y(x)):
dsolve(ode); #hangs

I noticed that in Maple 2019.2 this problem is also there. But not in Maple 2019.  So something changed from after Maple 2019.

Here is worksheet on Maple 2018 that shows these worked there. But no longer work on Maple 2020. There might be more like these but these the ones I found so far.




issue.mw

Why 

evalf(evalf(''Pi''))

Produces 

But

evalf(''Pi''):
evalf(%)

Produces

      3.141592654

 

 

Could some Maple expert please explain this strange behavior of int? Using Maple 2020 on windows 10



Same integrand. But in one case exp(arcsin(x)) and in another exp(1)^arcsin(x). Why one worked and not the other?

Here is the code

restart;
integrand1 := (x^3*exp(arcsin(x)))/sqrt(1 - x^2);
integrand2 := (x^3*exp(1)^arcsin(x))/sqrt(1 - x^2);
simplify(integrand1-integrand2);
int(integrand1,x);
int(integrand2,x)

 

Download bug.mw

 

 

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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