Perhaps a bug in matlab?

Hello friends!

I think I have encountered a bad issue about matlab, perhaps it is a bug. Consider the following commands

>> syms x x0 a b

>> f=int(1/(a+b*x),x)

f =log(a + b*x)/b

but now, trhe following command does not give me the result it should (it feels as if matlab is unable to solve this easy integration)

>> f=int(1/(a+b*x),x,x0,x)

f =int(1/(a + b*x), x, x0, x)

and I have to fix this by the command f=int(1/(a+b*x),x);f=f-subs(f,x,x0). Note that, in some other cases matlab does the job correctly, for instance:

f=int(sin(x),x,x0,x)

f =cos(x0) - cos(x)

It took a rather long time for me to understand why my code (not these stuff. I am talking about a very big code where these stuff were just a tiny part of it) does not produce the result it must produce.

I hope matlab developers really correct such bugs! Very annoying part is that matlab is not free and has such problems!!!

Answer 1

[Walter Roberson]

It is correct that it should not be giving you the solution. Your equations do not account for the possibility that you might be integrating through a discontinuity.

syms x x0 a b real
f = int(1/(a+b*x), x, x0, x, 'ignoreanalytic', true)

f =