derivative problem

[sialoproject]

f(x) = 5 inverse sin (x/4)

I did the math and I keep getting

20/ (16-x^2) but it says the right answer on the top is a 5, not 20.
I'm not sure where I'm getting my math wrong. can someone work it out?

 

[Deleted member 4993]

f(x) = 5 inverse sin (x/4)

I did the math and I keep getting

20/ (16-x^2) but it says the right answer on the top is a 5, not 20.
I'm not sure where I'm getting my math wrong. can someone work it out?

Please post your work so that we can find your mistake.

May be you want start ona slightly different path:

\(\displaystyle y \ = \ 5sin^{-1}(\frac{x}{4})\)

substitute:

u = x/4

\(\displaystyle y \ = \ 5sin^{-1}(u)\)

Using chain rule:

\(\displaystyle \frac{dy}{dx} \ = \ \frac{dy}{du} \ * \ \frac{du}{dx}\)

Now continue.....