Answer
$ 1-\sqrt 2$
Work Step by Step
$tan(\frac{7\pi}{8})=\frac{1-cos(\frac{7\pi}{4})}{sin(\frac{7\pi}{4})}=\frac{1-\frac{\sqrt 2}{2}}{-\frac{\sqrt 2}{2}}=1-\sqrt 2$
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