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These are questions asked by briceM

I am trying to do the following double integral in tranches as listed here:

P := proc (x, y) options operator, arrow; (1/2)*exp(-(1/2)*(x^2+G*y^2-2*B*x*y)/(-B^2+G))/(Pi*sqrt(-B^2+G)) end proc

Since G and B are constant

((int(x = 0 .. infinity))*(int(y = -infinity .. 0))+(int(x = -infinity .. 0))*(int(y = 0 .. infinity)))*P(x, y)

But does notwork. How do I pass these coordinates to polar?


Hi, i try the part of Real of the complex expression:

w := A*exp(-alfa(1+I)*y)+B*exp((1+i)*y);
            A exp(-alfa(1 + I) y) + B exp((1 + i) y)
u := Re(w);
          Re(A exp(-alfa(1 + I) y) + B exp((1 + i) y))

But does not work.




Ho, I try series taylor of tanh, but I want that result is in function of tanh(sqrt(q)*z/y) and not exponential e.

f1 := taylor(tanh(sqrt(q)*z/y+x*m/y), m, 2)

f1 := ((exp(sqrt(q)*z/y))^2-1)/((exp(sqrt(q)*z/y))^2+1)+4*(exp(sqrt(q)*z/y))^2*x*m/(((exp(sqrt(q)*z/y))^2+1)^2*y)+O(m^2)


That is, it should look like:




Hi, I´m try take out common factor with "collect"

collect(-(1/4)*G*r^2/eta-(1/4)*G*(ri^2-ro^2)*ln(r)/(eta*(ln(ri)-ln(ro)))-(1/4)*G*(ln(ri)*ro^2-ri^2*ln(ro))/(eta*(ln(ri)-ln(ro))), -(1/4)*G/eta)

  But this does not work well.



Hi, I try this numerical integral with:
int((1/2)*exp(-(1/2)*z^2)*Jo*sqrt(2)*(1-tanh(sqrt(q)*z/T)^2)/(sqrt(Pi)*T), z = -infinity .. infinity, numeric)
But does not work.
I have also tried it without success with:

evalf(Int((1/2)*exp(-(1/2)*z^2)*Jo*sqrt(2)*(1-tanh(sqrt(q)*z/T)^2)/(sqrt(Pi)*T), z = -infinity .. infinity, method = _d01amc, methodoptions = [maxintervals = 1000]))
How can i do?

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