A signal K cos(ωt) is given as an input to real causal linear time-invariant system. The steady-state output of the system for this input is obtained as L cos (ηt + ϕ). With K, L, ω, η, ϕ as constants, which of the following is true?
1
L is equal to K, and η need not be equal to ω
2
L is equal to K, and η is equal to ω
3
L need not be equal to K, and η need not be equal to ω
4
L need not be equal to K, and η is equal to ω