What's wrong with my arc tangens calculation?

[Laszlo Nagy]

> but when i lookup tg in a paper table (last decade math book) i've got these values:
>
> tg(63'10'') = 1.9768
> tg(63'20'') = 1.9912
> tg(63'30'') = 2.0057
>
> For me python should return something more like 63'2x'' than 63'4x''(becasue 63'30'' is higher than 2.0)
>
> what's wrong?
>
63° 30" is 63.5°. So nothing is wrong. (You know, 1° = 60 arc second!)