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Mathematics 14 Online
OpenStudy (anonymous):

need help on the attachment

OpenStudy (anonymous):

OpenStudy (anonymous):

\[y=\sqrt{x}e^{x^2-x}(x+1)^{\frac{3}{2}}\]right?

OpenStudy (anonymous):

take the log, rewrite using properties of the log, find the derivative, and then multiply back by the original funciton

OpenStudy (anonymous):

wrong problem I meant to put up different problem, sorry

OpenStudy (anonymous):

\[\ln(\sqrt{x}e^{x^2-x}(x+1)^{\frac{3}{2}}\] \[\ln(\sqrt{x})+\ln(e^{x^2-x})+\frac{3}{2}\ln(x+1)\]

OpenStudy (anonymous):

oops ok

OpenStudy (anonymous):

OpenStudy (anonymous):

That the actually problem, the one you solve I knew how to do already

OpenStudy (anonymous):

ok well this is rather a silly problem but we can do it i think \[\frac{x}{|x|}=1\text { if } x > 0\] and \[\frac{x}{|x|}=-1\text { if } x < 0\] use \[g(x)=x^2,f(x)=\sqrt{x}\] and the chain rule to find the derivative of \[f\circ g(x)=\sqrt{x^2}\] you get \[(f\circ g(x))'=f'(g(x))\times g'(x)=\frac{1}{2\sqrt{x^2}}\times 2x=\frac{x}{\sqrt{x^2}}=\frac{x}{|x|}\]

OpenStudy (anonymous):

what there was a problem of finding the derivative of g(x) =sin⁡|x| or f(x) = |sin⁡x|

OpenStudy (anonymous):

you mean by the chain rule?

OpenStudy (anonymous):

yeah

OpenStudy (anonymous):

ok well for \[f(x)=|\sin(x)|\] then you should really say \[f(x) = |\sin(x)| = \left\{\begin{array}{rcc} \sin(x) & \text{if} & \sin(x) \geq 0 \\ -\sin(x)& \text{if} & \sin(x) < 0 \end{array} \right. \]

OpenStudy (anonymous):

so the derivative will be \[\cos(x)\] or \[-\cos(x)\] depending on the interval

OpenStudy (anonymous):

but if you want to do it as the chain rule using what you have above, you could say \[f'(x)=\frac{\sin(x)\cos(x)}{|\sin(x)|}\] which really just says the same thing

OpenStudy (anonymous):

since \[\frac{\sin(x)}{|\sin(x)|}\] is either 1 or -1

OpenStudy (anonymous):

why 1 or -1. are you dividing sin by sin

OpenStudy (anonymous):

right. it is either 1 or -1 because |sin(x)| is either sin(x) or - sin(x) depending on whether sine is positive or negative

OpenStudy (anonymous):

so if sin(x) is positive then sin(x)/|sin(x)|=1 and if sin(x) is negative then sin(x)/|sin(x)|=-1

OpenStudy (anonymous):

ok, so what about If g(x) =sin⁡|x|

OpenStudy (anonymous):

then by the chain rule you get \[g'(x)=\cos(|x|)\times \frac{x}{|x|}\] and again the second part is either 1 or -1 depending on whether x is positive or negative

OpenStudy (anonymous):

so how would the combine form of that look like?

OpenStudy (anonymous):

not sure what you mean

OpenStudy (anonymous):

What happen to the cosine on the numerator for last problem you did

OpenStudy (anonymous):

you mean \[g'(x)\]?

OpenStudy (anonymous):

f'(X)

OpenStudy (anonymous):

it is \[g'(x)=\frac{x\cos(|x|)}{|x|}\] of

OpenStudy (anonymous):

\[f'(x)=\frac{\sin(x)\cos(x)}{|\sin(x)|}\]the cosine is still there. so it is either cosine or - cosine depending on whether sine is positive or negative

OpenStudy (anonymous):

oh, ok thanks again satellite

OpenStudy (anonymous):

yw

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