In case of reciprocating engines the ratio of primary to secondary forces is

(a) \(\cos \theta / \cos 2 \theta\)

(b) \(\cos \theta /(\mathrm{n} \cos 2 \theta)\)

(c) \(n \cos \theta / \cos 2 \theta\)

(d) \(\cos ^{2} \theta / \cos 2 \theta\)