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Mathematics 17 Online
OpenStudy (3psilon):

Help with derivatives

OpenStudy (3psilon):

\[\frac{x }{ \sqrt{1-x^{2} }} \]

OpenStudy (3psilon):

I keep messing up and getting the wrong answer!

OpenStudy (lgbasallote):

this looks like a job for quotient rule

OpenStudy (lgbasallote):

so you know your denominator is just squared \[\huge \implies \frac{numerator}{1 - x^2}\] agree?

OpenStudy (3psilon):

yes

OpenStudy (baldymcgee6):

\[y = \frac{ x }{ \sqrt{1-x^2} }\]\[y' = \frac{ g'h-gh' }{ h^2 } where \frac{ g(x) }{ h(x) }\]

OpenStudy (lgbasallote):

then for the first part of the numerator... you copy the denominator and take the derivative of the numerator so.. \[\sqrt{1-x^2} \times d(x) \implies \sqrt{1-x^2} \times 1 \implies \sqrt{1 - x^2}\] did you get this part?

OpenStudy (3psilon):

yes

OpenStudy (lgbasallote):

then for the second part...copy the numerator then diffeerntiate the denominator \[x \times d(\sqrt{1-x^2})\] this is chain rule... \[x \times \frac{1}{2\sqrt{1-x^2}} \times (-2x)\] is this what you got?

OpenStudy (3psilon):

Following

OpenStudy (lgbasallote):

so... now... simplify that last part i wrote

OpenStudy (3psilon):

It is the adding the fractions with the square roots that are messing me up

OpenStudy (lgbasallote):

simplify that last part i wrote first...

OpenStudy (3psilon):

kk

OpenStudy (3psilon):

\[-2x^{2}/2(1-x)^{3/2}\]

OpenStudy (lgbasallote):

how did you get (1-x)^3/2

OpenStudy (3psilon):

I forgot the x^2

OpenStudy (3psilon):

But isn't the derivative of \[(1-x^{2})^{1/2} == \frac{ 1 }{ 2 }(1-x^{2})^{3/2} * -2x \] @lgbasallote

OpenStudy (lgbasallote):

...are you mixing this with integration?

OpenStudy (3psilon):

I meant -3/2

OpenStudy (3psilon):

Ohhh Crap

OpenStudy (3psilon):

I thought it was ^-1/2

OpenStudy (3psilon):

SOrry

OpenStudy (lgbasallote):

\[\Large \frac d{dx} (\sqrt x) \implies x^{\frac 12} \implies \frac 12 x^{\frac 12 - \frac 22} \implies \frac 12 x^{-\frac 12}\]

OpenStudy (3psilon):

Yes my bad! . okok

OpenStudy (lgbasallote):

so simplify \[x \times \frac 1{2\sqrt{1-x^2}} \times (-2x)\] again

OpenStudy (3psilon):

\[\frac{ -2x^{2} }{ 2(\sqrt{1-x^{2}}}\]

OpenStudy (3psilon):

@lgbasallote

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