Which of the following statements are always correct, where Q denotes the set of rational numbers?
(1) cos2θ∈Q and sin2θ∈Q⇒tanθ∈Q, if defined
(2) tanθ∈Q⇒sin2θ, cos2θ, and tan2θ∈Q, if defined
(3) If sinθ∈Q and cosθ∈Q, then tan3θ∈Q, if defined
(4) If sinθ∈Q, then cos3θ∈Q