If you want to ignore `Abs`, replace it: `expr.replace(Abs, Id)`
/c
On Wednesday, December 21, 2022 at 10:13:22 PM UTC-6 arthur...@gmail.com
wrote:
> Staffan,
>
> Just a guess, but sin(phi) goes negative even for positive values of phi.
> You’d have limit the range to 0 <= phi <= pi.
>
> — Arthur
>
> On Mon, Dec 19, 2022 at 1:41 PM Staffan Lundberg <drstaffan...@gmail.com>
> wrote:
>
>> I am working with curvilinear coordinates, especiallt how to determine
>> scale factors for spherical coordinates and how to express the unit vectors
>> i terms of i, j, k (cartesian base vectors). I submit some code
>>
>> #
>> # curvilinear.py
>> #from sympy import *
>> x, y, z = symbols("x y z")
>> rho= symbols("rho",positive=True,real=True)
>> theta = symbols("theta",positive=True,real=True)
>>
>> phi = symbols("phi",positive=True,real=True)
>> # spherical coord
>> x=rho*sin(phi)*cos(theta)
>> y=rho*sin(phi)*sin(theta)
>> z=rho*cos(phi)
>>
>> A=Matrix([[x],[y],[z]])
>> r=A
>> dr=diff(r,rho)
>> hr=dr.norm()
>> hr=simplify(hr)
>>
>> dphi=diff(r,phi)
>> hphi=dphi.norm()
>> hphi=simplify(hphi)
>>
>> dtheta=diff(r,theta)
>> htheta=dtheta.norm()
>> htheta=simplify(htheta)
>>
>> r_hat=dr/hr
>> fi_hat=dphi/hphi
>> th_hat=dtheta/htheta
>> print(fi_hat)
>> print(th_hat)
>> print(r_hat)
>> #
>> #
>>
>> Problems with th_hat. Despite telling sympy that phi is positive, I get
>> Abs(sin(phi)) instead of sin(phi). Thus python does not cancel the
>> factor sin(phi).
>>
>> Has anyone some hints how to solve this issue. Maybe a bug in sympy?
>> /Staffan L
>>
>> --
>> You received this message because you are subscribed to the Google Groups
>> "sympy" group.
>> To unsubscribe from this group and stop receiving emails from it, send an
>> email to sympy+un...@googlegroups.com.
>> To view this discussion on the web visit
>> https://groups.google.com/d/msgid/sympy/717dfd84-7b24-4a28-83c5-19ba7ca53e97n%40googlegroups.com
>>
>> <https://groups.google.com/d/msgid/sympy/717dfd84-7b24-4a28-83c5-19ba7ca53e97n%40googlegroups.com?utm_medium=email&utm_source=footer>
>> .
>>
>
--
You received this message because you are subscribed to the Google Groups
"sympy" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to sympy+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/sympy/ad627534-58eb-4001-a76f-2aad0d6f16e8n%40googlegroups.com.
