How do you evaluate $arctan (- 1)$ $arctan(-1)$ without a calculator?

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Answer 1 · 2017-03-21T04:59:43

$x = arctan (- 1)$ $x=arctan(-1)$

$tan x = - 1$ $tanx=-1$

Wikipedia

Think of where on the unit circle is tangent of some angle equal to -1.

$x = \frac{- π}{4} + π n$ $x=(-pi)/4+pin$

How do you evaluate arctan(-1)arctan(−1)arctan(-1) without a calculator?