How do you evaluate $arccost(-sqrt3 /2)$ ?

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Answer 1 · 2015-07-12T16:21:56

Find $arccost ((-sqrt3)/2)$

Trig table gives ->

$cos t = (-sqrt3/2)$ --> arc $t = (5pi)/6$ or 150 deg

Trig unit circle gives another arc t that has the same cos value.

$t = - (5pi)/6 or (7pi)/6$

Answer: within period $(0, 2pi)$ , there are 2 answers: $(5pi)/6 and (7pi)/6$

How do you evaluate arccost(-sqrt3 /2) arccost(-sqrt3 /2) ?