Given four trapeziums ABCD where the bases 
and 
, and the length of the side 
.
In the first trapezium, the non-parallel sides intersect at the point E. Calculate the length of the distance DE.
In the second trapezium, the size of the angle 
is equal to 
. Calculate the size of the angle 
. Round the result to the nearest minute.
In the third trapezium, the diagonal BD measures 
. Calculate the length of 
.
In the fourth trapezium, the size of the angle 
is equal to 
. There is a point T on the side AD and a point V on the side AB such that 
. Calculate at what length 
the area of the triangle VBT will be maximum.
