On 13 February 2016 at 07:48, Nasir Haniffa <nasirhani...@gmail.com> wrote:
> Hi,
>
> How to get the correct answer for the problems
>
> 1. Integral( (1+x**2)**(-3/2) ,(x,-1,1) )
>
>
> 2. Integral( (1+x**2+y**2)**(-3/2) ,(x,-1,1), (y,-1,1) )
>
> Both gives 0 in sympy which is wrong.
This is a bug in current master:
>>> from sympy import Symbol, Integral
>>> x = Symbol('x')
>>> Integral( (1+x**2)**(-3/2) ,(x,-1,1) )
Integral((x**2 + 1)**(-2), (x, -1, 1))
>>> Integral( (1+x**2)**(-3/2) ,(x,-1,1) ).doit()
1/2 + pi/4
Note that -3/2 under Python 2.7 gives -2 which is not what you want so
use -S(3)/2
>>> from sympy import S
>>> Integral( (1+x**2)**(-S(3)/2) ,(x,-1,1) ).doit()
0
>>> expr = (1+x**2)**(-S(3)/2)
>>> expr.integrate((x, -1, 1))
0
Under sympy 0.7.1 I get:
>>> Integral( (1+x**2)**(-S(3)/2) ,(x,-1,1) ).doit()
Integral((x**2 + 1)**(-3/2), (x, -1, 1))
>>> Integral( (1+x**2)**(-S(3)/2) ,(x,-1,1) ).evalf()
1.41421356237310
--
Oscar
--
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 post to this group, send email to sympy@googlegroups.com.
Visit this group at https://groups.google.com/group/sympy.
To view this discussion on the web visit
https://groups.google.com/d/msgid/sympy/CAHVvXxTXY-w1_VfHBqPZmTZkPGrM1T4T8md5pMh5wraXmt-KeQ%40mail.gmail.com.
For more options, visit https://groups.google.com/d/optout.
