Question

Find the value of sgn(-1) + sgn(0) + sgn(1), where sgn$\left(x\right)$ is the signum function

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Answer 1

$\text{sgn}\left(x\right)=\{\begin{array}{cc}1,& ifx>0\\ 0,& ifx=0\\ -1& ifx<0\end{array}$
is called the signum function.
The domain of the signum function is R and the range are the set {-1, 0, 1}
The graph of signum function is

sgn(-1) = -1
sgn(0) = 0
sgn(1) = 1
Therefore sgn(-1) + sgn(0) + sgn(1) = -1 +0 +1 = 0