dharr

Dr. David Harrington

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21 years, 232 days
University of Victoria
Professor or university staff
Victoria, British Columbia, Canada

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I am a retired professor of chemistry at the University of Victoria, BC, Canada. My research areas are electrochemistry and surface science. I have been a user of Maple since about 1990.

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These are replies submitted by dharr

@acer So Maple 2026 misses some, but Maple 2025 finds some that are not actually solutions.

restart;

kernelopts(version);

`Maple 2025.2, X86 64 WINDOWS, Nov 11 2025, Build ID 1971053`

eq:=x^Pi-Pi^x;

x^Pi-Pi^x

S:=solve(eq, x, allsolutions);

exp(-LambertW(_Z3, -(ln(Pi)+(2*I)*Pi*_Z4)*exp(-(2*I)*_Z1)/Pi)-(2*I)*_Z1)

A real solution on the principal branch

eval(S,{_Z3=0,_Z4=0,_Z1=0});
x=evalf(%);
simplify(fnormal(evalf(eval(eq,x=%%))),zero);

exp(-LambertW(-ln(Pi)/Pi))

x = 2.382179085

-0.1e-7

Pi is on the +1 branch ...

eval(S,{_Z3=1,_Z4=-1,_Z1=0});
x=simplify(fnormal(evalf(%)),zero);
simplify(fnormal(evalf(eval(eq,x=%%))),zero);

exp(-LambertW(1, -(ln(Pi)-(2*I)*Pi)/Pi))

x = 3.141592654

0.

... or -1 with different _Z4

eval(S,{_Z3=-1,_Z4=1,_Z1=0});
simplify(fnormal(evalf(%)),zero);
simplify(fnormal(evalf(eval(eq,x=%%))),zero);

exp(-LambertW(-1, -(ln(Pi)+(2*I)*Pi)/Pi))

3.141592654

0.

A complex solution

eval(S,{_Z3=-1,_Z4=0,_Z1=1});
x=simplify(fnormal(evalf(%)),zero);
simplify(fnormal(evalf(eval(eq,x=%%))),zero);

exp(-LambertW(-1, -ln(Pi)*exp(-2*I)/Pi)-2*I)

x = 6.368931094+7.945243820*I

0.10e-4-0.16e-5*I

But some combinations of _Z3, _Z4 and _Z1 are not solutions

eval(S,{_Z3=-1,_Z4=1,_Z1=1});
x=simplify(fnormal(evalf(%)),zero);
simplify(fnormal(evalf(eval(eq,x=%%))),zero);

exp(-LambertW(-1, -(ln(Pi)+(2*I)*Pi)*exp(-2*I)/Pi)-2*I)

x = 1.047180350+.1618339307*I

-2.196184021-0.550772690e-1*I

eq2 := eval(eq, x = s + t*I);
eqs := evalc([(Re, Im)(eq2)]);

(s+I*t)^Pi-Pi^(s+I*t)

[exp((1/2)*Pi*ln(s^2+t^2))*cos(Pi*arctan(t, s))-exp(s*ln(Pi))*cos(t*ln(Pi)), exp((1/2)*Pi*ln(s^2+t^2))*sin(Pi*arctan(t, s))-exp(s*ln(Pi))*sin(t*ln(Pi))]

There are many complex solutions, which come in complex conjugate pairs.

plots:-implicitplot(eqs, s = -10 .. 10, t = -10 .. 10, color = [red, blue], labels = [Re(x), Im(x)], gridrefine = 4);

NULL

Download s_ex.mw

@acer @Alfred_F In Maple 2026 (but not in Maple 2024) convert(simplify(convert(z, cosh)), cosh); works.

I guess my point was that I would not expect eval to work with infinity, and I always use limit with infinity (for the reason that @sand15 mentioned: they are different things). Elsewhere in Maple infinity is handled slightly differently to mathematics, e.g., a*infinity is left as is until simplify(a*infinity) assuming a>0 leads to infinity. But I think this is fairly well thought out and generally doesn't lead to inconsistencies. Another principle that is often found in Maple is that if something is going to be fairly compute intensive it may not be done by default but you can force it with an option or another command. Here I do not think you want to overload eval with special cases since then writing efficient code for long calculations in a loop degrades performance.

@C_R @nm I guess with infinity it is safer to routinely use limit.

A workaround is to use expand

eval(expand((A*x-1)/x),x=infinity);

But it is hard to see any reason to get zero here. Many other places Maple gives sensible results with infinity. For example, infinity/infinity gives undefined, which would be a better result here than zero.

The fractional powers are very hard to deal with. I think you have to transform your ode to get rid of them

simplify(PDEtools:-dchange(V(xi) = U(xi)^3, Fode, [U(xi)])) assuming U(xi) >0

Of course if you really want V(xi) negative there is a mathematical problem about which cube root you want, but I'm guessing the equation was produced with the same disregard for rigor.

I'm struggling to understand the meaning here. It seems you want x=1 at t=0 since the units of the upper and lower limits should be the same and the integral should go to zero at t=0 (from the rhs). But in your approximation for x(t) you have ln(t) which implies you want t=1 to be the initial time?

In your mimimization you minimized t. Probably you meant to mimimize the integral of the squared difference over some range of t? 

Under my guessed interpretation, there is an easy solution:

intsolve.mw

These are not files listed on the File format help page, so you are out of luck for an easy way. I guess if you know the details of the binary file you could write a routine to read them, but I don't think that would count as "easy". 

Just installed 2026.0 in windows 11; run as administrator to install; didn't import previous preferences. All is working fine.

@KIRAN SAJJAN A quick look suggests it is reasonable, assuming the R1(z) and R2(z) functions are correct. I believe you said the BCs depended on z, but I do not see that dependence, though it might be implicit.

@Suryakanth @KIRAN SAJJAN You set up the odes for other conditions, so why not set up for different R or z and solve them? Sorry, I don't understand what you want.

@KIRAN SAJJAN Sorry, the equations you provided do not contain z, so I'm confused. Do you mean it is another independent variable, and you want to solve a PDE? (I don't want to read and figure out the paper.)

@WD0HHU This seemed to be fixed in 2025.2

@salim-barzani Use a set for the 3 plots otherwise it will think it is a parametric plot.

Dr.D-N.mw

You can directly use the procedure for w(eta) returned by dsolve to evaluate w(0.999) etc and the integrals.

parentartery_and_daughter_artery_error.mw

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