3.4.1 Mathematical representation of linear systems Letting the left-hand side of eq. 3.10) be zero dolt 2x(t)+ then the right-hand side of eq ( 3.10) must also be zero 0 y(t)+ t Solving the equation yields yoe J(at+o where is the phase shiftLetting the left-hand side of Eq. (3.10) be zero, then the right-hand side of Eq. (3.10) must also be zero, Solving the equation yields: where φ is the phase shift. 3.4.1 Mathematical representation of linear systems ( ) ( ) 0 2 2 2 + = dt d x t  x t ( ) ( ) 0 2 2 2 + = dt d y t  y t ( ) ( + ) = j t y t y e0