nm

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These are questions asked by nm

What is the reason Maple likes to do this

arccos(sin(x));

         Pi/2 - arcsin(sin(x))

Both are correct, but the first has leaf count of only 3 and the second expression has leaf count of 11.

Surely the first is simpler to look at and read so the second form is not simpler.

What is the logic behind this automatic transformation? And did Maple always do this?

Found integration problem which causes server.exe to crash each time. I hope this can be used to help find why server.exe keeps crashing much more than before in Maple 2022.

 

This happens each time. The above is a typical example of what I have been saying all the time above server.exe crashing. It should not do that. If it can not solve the problem, it should simply return.

I hope these problems will be fixed in Maple 2023.

Any one can figure why it crashes?

Attached worksheet.


 

interface(version);

`Standard Worksheet Interface, Maple 2022.2, Windows 10, October 23 2022 Build ID 1657361`

restart;

integrand:=(2*x^2022+1)/(x^2023+x);
int(integrand,x);

(2*x^2022+1)/(x^2023+x)


 

Download crash_feb_3_2023.mw

 

I am converting some code from Mathematica. In it there is this solution

eqs={2c2+c0==1,6c3+2c1==2,3c2+12c4==1};
FindInstance[eqs,{c0,c1,c2,c3,c4}]

Which gives

{{c0 -> 0, c1 -> 0, c2 -> 1/2, c3 -> 1/3, c4 -> -(1/24)}}

Maple's solve gives

eqs := [2*c2 + c0 = 1, 6*c3 + 2*c1 = 2, 3*c2 + 12*c4 = 1];
sol:=solve(eqs, {c0, c1, c2, c3, c4})

Gives

sol := {c0 = 1/3 + 8*c4, c1 = -3*c3 + 1, c2 = 1/3 - 4*c4, c3 = c3, c4 = c4}

I know that both are correct solutions. But I'am asking if there is a command or an option I overlooked that will generate the same result as the above from FindInstance, which will make it easier for me.

May be there is another solver package or command I could try?

I am not sure what algorithm FindInstance uses. The documentation page does not say.

I have only seen big O show up in series solutions, as in 

series(sin(x),x)

I've never seen it before show up in result of solve

restart;
eq:=x=p*(a*ln(p+sqrt(p^2-2))+2*_C1)/(2*sqrt(p^2-2));
sol:=solve(eq,p);

What does it actually mean when the solution has  O(RootOf(....))?  

Should not result of solve be exact? isn't having big O means an approximation?

Maple 2022.2 on windows 10

Could you suggest a more elegent way to remove any entry in piecewise which has undefined in it?

expr:=(s+exp(-Pi*s)-exp(-2*Pi*s))/(s*(s^2+2*s+2));
inttrans:-invlaplace(expr,s,t);
Y:=convert(%,piecewise);
#remove all entries in piecwise which has undefined

To obtain this

I can;t just apply select on piecewise. So currently I convert piecwise to list of lists, each sublist has the 2 entries you see above in each row.

Next apply select. Then use piecewise again on the result. This works, but wondering if there is a better way.

Attached worksheet.

interface(version);

`Standard Worksheet Interface, Maple 2022.2, Windows 10, October 23 2022 Build ID 1657361`

restart;
expr:=(s+exp(-Pi*s)-exp(-2*Pi*s))/(s*(s^2+2*s+2));
inttrans:-invlaplace(expr,s,t);
Y:=convert(%,piecewise);
#remove all entries in piecwise which has undefined

expr := (s+exp(-Pi*s)-exp(-2*Pi*s))/(s*(s^2+2*s+2))

exp(-t)*sin(t)+(1/2)*(-1+exp(-t+2*Pi)*(cos(t)+sin(t)))*Heaviside(t-2*Pi)+(1/2)*(1+exp(-t+Pi)*(cos(t)+sin(t)))*Heaviside(t-Pi)

piecewise(t < Pi, exp(-t)*sin(t), t = Pi, undefined, t < 2*Pi, exp(-t)*sin(t)+1/2+(1/2)*exp(-t+Pi)*(cos(t)+sin(t)), t = 2*Pi, undefined+(1/2)*exp(-Pi), 2*Pi < t, exp(-t)*sin(t)+(1/2)*exp(-t+2*Pi)*(cos(t)+sin(t))+(1/2)*exp(-t+Pi)*(cos(t)+sin(t)))

Y:=[op(Y)]:
Y:=seq([Y[n],Y[n+1]],n=1..nops(Y)-1,2):
ListTools:-Flatten(select(not has,[Y],'undefined')):
piecewise(op(%))

piecewise(t < Pi, exp(-t)*sin(t), t < 2*Pi, exp(-t)*sin(t)+1/2+(1/2)*exp(-t+Pi)*(cos(t)+sin(t)), 2*Pi < t, exp(-t)*sin(t)+(1/2)*exp(-t+2*Pi)*(cos(t)+sin(t))+(1/2)*exp(-t+Pi)*(cos(t)+sin(t)))


Download remove_undefined.mw

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