Question

How do you find the exact value of cos(arcsin(-1/4))#?

Answer 1

`sqrt15/4`, in exactitude. This is 0.968245836, nearly.

Explanation:

Let `a = arc sin (-1/4) in Q4`, wherein cosine is positive. Then,

`sin a = -1/4` and the given expression

`cos a = sqrt(1-sin^2a) = sqrt(1-1/16) = sqrt 15/4`.