If `cos (2 sin^(-1) x) = (1)/(9)`, then find the value of x

1.	If `cos (2 sin^(-1) x) = (1)/(9)`, then find the value of x
Answer» Let `sin^(-1) x = theta`. Then, `cos 2 theta = (1)/(9)` or `1 - 2 sin^(2) theta = 9` or `1 - 2x^(2) = (1)/(9)` or `x^(2) = (4)/(9)` or `x = +-(2)/(3)`

Discussion

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