# Question about step function

1. Apr 7, 2013

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2. Apr 7, 2013

### CompuChip

The basic definition is
$$u(t) = \begin{cases} 0 & t < 0 \\ 1 & t > 0 \end{cases}$$
(and usually it's defined as u(0) = 1/2, but let's ignore that for now).

So the shifted step function is 1 only if t - a > 0, which means if t > a.

From your graph I gather that you want a function which is 1 if -2 < x < 0 and 0 otherwise. You can easily verify your answer x(t) = u(t + 2) - u(t) by considering the regions x < -2, -2 < x < 0 and x > 0 separately.
E.g. what do x(-3), x(-1) and x(1) work out to?