How do you evaluate $cos(arcsin(-1/4))$ ?

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Answer 1 · 2015-07-13T05:14:49

Evaluate $cos (arcsin (-1/4))$

Calculator gives:
$sin x = - 1/4 = - 0.25$ --> Calculator gives:

a. $x = - 14.48$ deg
Trig unit circle gives another arc x that has the same sine value:
b. $x = 180 + 14.48 = 194.48$ deg

Answers:
cos (-14.48) = cos (14.48) = 0.97
cos (194.48) = - 0.97

How do you evaluate cos(arcsin(-1/4))cos(arcsin(-1/4))?