SO here is the formula:

=ROUND(IF(X=0;SI(Y=0;"this wind as no favorite
direction";IF(Y0;90;-90));ATAN(Y/X)*180/PI()+IF(X<0;180;0));1)

I let you make cos and sin means (represented in this formula by x and
y) I use other cells for that purpose this make the formula readable and
also gives excel less job (because if you repeat a formula inside an
other formula i suppose he needs to make the same job many times) OF
course you can mask the unneeded cells.

for x or for y you may use matrix formula if you konw them:
=MEAN(SIN(MyDataRange*PI()/180)) in one cell and validate it with
CTRL+SHIFT+ENTER

with this you do not need to have 2 colmuns of sin and cos