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5:42 AM

Anyone knows how to access via URLDownload a file in my private GitHub repo? The Authentication option does not seem to work.

3 hours later…

Raphael J.F. Berger

9:05 AM

Dear all, it seems I am making a stupid mistake, I try to resubstitute Replace[Grad[rho[r],{x,y,z}],Sqrt[x^2+y^2+z^2]->r ]

but it doesnt work.

I used: r=Sqrt[x^2+y^2+z^2]

4 hours later…

anhnha

12:43 PM

@RaphaelJ.F.Berger just some reference:
https://mathematica.stackexchange.com/questions/3463/replacing-composite-variables-by-a-single-variable

2 hours later…

newUser

2:49 PM

Q: Simplification and numerical evaluation differs substantially

My question is very simple. I am trying to simplify an expression that I was expecting to be vanishing. However, If I numerically evaluate the expression I find 1, whereas if I simplify it I get 0, see the picture Here's the code to reproduce it (m Sqrt[P + Sqrt[m^2 + P^2]] - Sqrt[-P + Sqrt[m^2 ...