How do you evaluate $tan(tan^-1(2/sqrt7))$ ?

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Answer 1 · 2016-11-28T15:34:30

$2/sqrt7$

$tan^-1 (2/(sqrt7)) -> arctan (2/sqrt7)$ -> arc t (whose tan is (2/sqrt7))
There for:
$tan (tan^-1 tan (2/sqrt7))$ --> $tan (t) = 2/sqrt7$

How do you evaluate tan(tan^-1(2/sqrt7))tan(tan^-1(2/sqrt7))?