finding the extreme values for inverse sine x - 2x

[etidd]

hello, this is the second one i'm stumped on.

f(x) = inv. sin x - 2x

f '(x) = 1/(sqrt.(1 + x^2)) - 2

now i don't know what to do.
the back of the book said the answer is +/- sqrt.(3)/2

how can you do this?

 

[Deleted member 4993]

hello, this is the second one i'm stumped on.

f(x) = inv. sin x - 2x

f '(x) = 1/(sqrt.(1 + x^2)) - 2

now i don't know what to do.
the back of the book said the answer is +/- sqrt.(3)/2

how can you do this?

Refer to your earlier post.