If a pentagon is regular, then all of the sides are the same length. This means that

So, if
, the lengths of the sides evaluate to

So, all the sides of the pentagon are 21 units long, and AB is 21 units long as well, because all sides are the same length.
This angle is "29 degrees 6 minutes 6 seconds".
-- There are 60 minutes in 1 degree.
So 1 minute = 1/60 degree.
-- There are 60 seconds in 1 minute.
So 1 second = 1/60 minute = 1/3600 degree.
29 6' 6" = (29)° + (6/60)° + (6/3600)°
= (29)° + (0.1)° + (0.001666...)°
= 29.101666...°
Rounded to the nearest thousandth of a degree: 29.102°