Half the angle of nip, (α), for a roll crusher is given by (where, dr, dp and df are diameters of crushing rolls, feed particles and rolls gap respectively) ?
A. cos α = (dr + dp)/(dr + df)
B. cos α = (dr + df)/(dr + dp)
C. tan α = (dr + dp)/(dr + df)
D. sin α = (dr + dp)/(dr + df)