=
,
i
=
=
Let x
= 1
arctg(1)
=
=
=
=
=
=
=
0
But
arctg(1)
=
An
explanation of the paradox:
The complex
logarithm is a multi-valued function.
Ln(z)
= ln|z|
+ i(arg
z
+ 2k
),
k
= 0, ±1, ±2, ...
Ln(1)
= ln|1| + i(arg
(1) + 2k
),
k
= 0, ±1, ±2, ...
If
we consider a branch Ln(1),
where
k
= 1 then
Ln(1) =
and the paradox disappears.
arctg(1)
=
=
= 
arctg(1)
= 
by
Tetyana Butler