We first prove that equation 3.2:
is the solution to the system of the following equations:
We assume here that the weight vector 
is a column vector
with the same dimensionality as 
.
At first we combine equations A.2, A.4 and A.5. They yield
We can further manipulate the norm appearing on the right hand side of the equation.
Here we have used the fact that 
.
The term 
does not depend on z, and therefore it can
be left out without affecting the minimisation. We can now rewrite
the system of equations:
Without the constraint 
the solution would be 
. It is evident that equation A.1 gives
the solution when we take the constraint into consideration.
