How do you evaluate $cos(-pi/6) cos (pi/4)$ ?

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Answer 1 · 2016-06-17T02:33:43

$sqrt6/4$

Trig table -->
$cos (pi/4) = sqrt2/2$
$cos (-pi/6) = cos (pi/6) = sqrt3/2$
$P = cos (pi/4).cos (-pi/6) = (sqrt2/2)(sqrt3/2) = sqrt6/4$

How do you evaluate cos(-pi/6) cos (pi/4)cos(-pi/6) cos (pi/4)?