Causal Systems
Definition: An LTI system that depends only on the present and past values of the input to the system. A system that is not causal depends on future values of the input to the system.
Examples: y(t) = x(t) + t + 2 - Causal because the input values are depending on the present time
$ y(t) = \int_t^\infty x(t) dt $
