how do i get tan(-1)

$$\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{tan}}{\left(-{\mathtt{1}}^\circ\right)} = -{\mathtt{0.017\: \!455\: \!064\: \!928}}$$

If you mean  $$\tan^{-1}$$  then select the 2nd button on the calculator first and use atan (which is the same thing).

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