function, zero for all negative values of the independent variable and equal to one for all positive values Note 1 to entry: See Figure 1 below for a graphical representation of ε(t). The value ε(0) may remain undefined or may be defined according to the context. Note 2 to entry: ε(x − x0) denotes a unit step at the value x0 of the independent variable x. Note 3 to entry: Notation H(x) is also used. Notation ϑ(t) is used for the unit step function of time. Notation ϒ(x) has also been used. Figure 1 – Graphical representation of ε(t)
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