Dr. Joshi and fellow users,

I have a very basic Black Scholes equation. The formula for call price is

C = S * N(d_1) - K * disc_factor * N(d_2)

The question is this : in the above formula, d_1 and d_2 depend on the value of the S. So, why is that fact ignored while deriving delta = del_C/del_S ? The well-known answer is of course N(d_1). What am I missing here?

Regards,

SR