Using Bessele in Maple returns zero

Question

I am so new in maple . I want to execute this this function on my formula as you can see in the below image :

As you can see every operations return zero .why ?

I am so new in maple

You probably typed zr when you meant to type z*r. Maple does not do implicit multiplication like that. — Jacques Carette, Aug 27 '16 at 17:07
This is one of the many cases why I find the 2D notation inferior to the Maple notation - it can be obscure. Your problem here is that zr is interpreted as the variable $zr$ and not $z\cdot r$. This is, however, a nice and intended feature as we are then not restricted to single-letter variables and functions. — Therkel, Aug 29 '16 at 08:31

score 0 · Accepted Answer · answered Aug 26 '16 at 10:08

0

Which version? Here are the inputs/outputs for Maple V or Maple 7, they should work with yours too:

diff(BesselI(a, z*r),r);
> (BesselI(a+1,z*r)+a/z/r*BesselI(a,z*r))*z

answered Aug 26 '16 at 10:08

gammatester

it is 18 ,let me check it – Ehsan Akbar Aug 26 '16 at 10:09
what is 'a' here in your solution? – Ehsan Akbar Aug 26 '16 at 10:10
Sorry I read $a$ instead of $o$ in your first example. If is actually a $0$ you get diff(BesselI(0, z*r),r) -> BesselI(1,z*r)*z – gammatester Aug 26 '16 at 10:13

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