What is the cosine of 13pi/6 and what other radian does it corresponds to?

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Answer 1 · 2015-04-22T23:54:00

$2pi = (12pi)/6$ corresponds to a full circle
so

$(13pi)/2 = (12pi)/6 +pi/6$

is equivalent to $pi/6$

Depending upon what you mean by "corresponds to"
$cos(x) = cos(-x)$

so
$cos((13pi)/6) = cos(pi/6) = cos(-pi/6)$

and in addition any angle which can be obtained from either of these by adding or subtracting an integer multiple of $2pi$ will also be equivalent.

$cos(pi/6)$ is the $cos$ of a standard right angled triangle with sides $1, sqrt(3), 2$
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$cos((13pi)/6) = sqrt(3)/2$