How do you evaluate $arccos (cos (\frac{13 π}{2}))$ $arccos(cos ((13pi)/2))$ ?

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Answer 1 · 2015-06-08T23:31:51

$cos (\frac{13 π}{12}) = cos (\frac{π}{12} + π) = - cos (\frac{π}{12}) = - 0.966$ $cos ((13pi)/12) = cos (pi/12 + pi) = - cos ((pi)/12) = - 0.966$

cos x = - 0.966 -> arc $x = 165$ $x = 165$ deg

How do you evaluate arccos(cos ((13pi)/2))arccos(cos(13π2))arccos(cos ((13pi)/2))?