Answer
1
Work Step by Step
period of $tan$ function is $\pi$
it means
$\tan \alpha =\tan \left( \pi +\alpha \right) $
$\tan \left( -135^0\right) =\tan \left( -\dfrac {3\pi }{4}\right) =\tan \left( -\dfrac {3\pi }{4}+\pi \right) =\tan \dfrac {\pi }{4}=1$
