Let us introduce 16 new numbers
to be the summations of terms cos(i*w), where i is and
element of Ai (Sets A1, A2,...A16 were defined previously). For example
The definitions of
(we already know the values of these numbers from the previous parts of
this page) show that these numbers are linear combinations of
.
For example
Hence, regarding
as unknown variables, we have 15 linear equations with 16 unknowns. We add one more equation (as the
first one):
We obtain a system of 16 equations. The matrix of this system is:
The determinant of this matrix is 34816, which is a product of a power of 2 and the number 17.
This is little surprising, since 17 is also a Fermat number just preceding the number 257. Because of
the value of determinant, the number 17 will occur in the next formulas.
The inverse matrix to the above matrix is:
Using this matrix it is easy to write formulas for .
For example, let us write a formula for i=10: