( ( ( Frequency and ) period ) ( ( are ( reciprocals ( of ( each other ) ) ) ) . ) )
(ROOT (S (NP (NN Frequency) (CC and) (NN period)) (VP (VBP are) (NP (NP (NNS reciprocals)) (PP (IN of) (NP (DT each) (JJ other))))) (. .)))
Frequency and period are reciprocals of each other.
(ROOT (S (NP (NP (DT The) (NN frequency)) (PP (IN of) (NP (DT a) (NN wave)))) (VP (VBZ is) (NP (NP (DT the) (NN reciprocal)) (PP (IN of) (NP (NP (DT the) (NN period)) (PP (IN of) (NP (DT the) (NN wave))))))) (. .)))