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How do I find the value of $cot(-240^o)$ ?

1 Answer

Aug 12, 2015

$cot(-240^o) = sqrt(3)/3$

Explanation:

$-240^o$ is equivalent to $120^o$

A $120^o$ is in Quadrant II with a reference angle of $60^o$

$60^o$ is a standard angle with $tan(60^o) = sqrt(3)$
$color(white)("XXXX")$ $color(white)("XXXX")$ $color(white)("XXXX")$ $rarr cot(60^o) = 1/sqrt(3) = sqrt(3)/3$

In Quadrant II, $tan$ (and, therefore, $cot$ ) is negative,

so
$color(white)("XXXX")$ $cot(-240^o) = -sqrt(3)/3$

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