# Derivative of y = x (1 - x^2)^1/2, is this correct?

1. Nov 14, 2004

### Leonidas

I keep on getting a weird answer when i take the dy/dx for this...
y=x(1-x^2)^1/2

i got x(1/x^2)^(-1/2)*-2x + (1-x^2)^(1/2)

... did i do that correctly?

Last edited: Nov 14, 2004
2. Nov 14, 2004

### kreil

$$y=x(1-x^2)^\frac{1}{2}$$

Use product rule/chain rule:

$$y=(x)(\frac{1}{2})(\frac{1}{\sqrt{1-x^2}})(-2x) + (1-x^2)^\frac{1}{2}$$

Slightly more simplified:

$$y=(\frac{-x^2}{\sqrt{1-x^2}}) + (1-x^2)^\frac{1}{2}$$

Pretty sure thats the answer...if so you aren't using the chain rule correctly. Double check how you get the derivitive of $$(1-x^2)^\frac{1}{2}$$

3. Nov 14, 2004

### Leonidas

DUH. *slaps self on forhead* .... heh... forgot a single step and it screwed me up (of course).

Thanks.

Last edited: Nov 14, 2004