Answer
$|z|=1$
see graph below
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Work Step by Step
See p. 602, Graphing Complex Numbers
The complex plane is determined by the real axis and the imaginary axis.
To graph the complex number a + bi, we plot the ordered pair of numbers (a,b) in this plane
See p. 603,
The modulus (or absolute value) of the complex number $z=a+bi$ is
$|z|=\sqrt{a^{2}+b^{2}}$
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Write z in the form a+bi:
$z=\displaystyle \frac{-\sqrt{2}}{2}+\frac{\sqrt{2}}{2}i$
Plot $(a,b)=(-\displaystyle \frac{\sqrt{2}}{2},\frac{\sqrt{2}}{2})$ in the complex plane
(see image, $\displaystyle \frac{\sqrt{2}}{2}\approx 0.707$).
$|z|=\sqrt{(-\frac{\sqrt{2}}{2})^{2}+(\frac{\sqrt{2}}{2})^{2}}=\sqrt{\frac{1}{2}+\frac{1}{2}}=1$
