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Mathematics 21 Online
OpenStudy (khally92):

Use the Implicit Function Theorem to find

OpenStudy (khally92):

\[dz/dy, given \sqrt{3y} -ycos(xz)=2x-3z^2\]

OpenStudy (khally92):

Its partial z partial y. noy dz/dy. Don't know how to write the partial partial thing

zepdrix (zepdrix):

\partial is the fancy d symbol :)

OpenStudy (khally92):

is the formula not \[dz/dy= -fy/fz\]

OpenStudy (khally92):

is it? so differentiating w.r.t.y you keep x and z constant

OpenStudy (khally92):

which gives \[3/2\sqrt{3y} - \cos(xz)\]

OpenStudy (khally92):

and w.r.t.z you keep x and y constant which gives \[xysin(xz) +6z\]

OpenStudy (khally92):

Is it?

OpenStudy (khally92):

\[-[3/\sqrt{3y}-\cos(xz)]/{xysin(xz)+6z}\]

OpenStudy (khally92):

Final answer?

OpenStudy (khally92):

@Loser66 @Michele_Laino

OpenStudy (loser66):

I don't know :)

OpenStudy (khally92):

KK thanks

OpenStudy (michele_laino):

I think that we have to apply the implicit functions theorem in the case of more than one dimension

OpenStudy (khally92):

Is this more than one dimension?

OpenStudy (michele_laino):

we have to define a function \(F\) such that: \[\large F\left( {x,y,z} \right) = \sqrt {3y} - y\cos \left( {xz} \right) - 2x + 3{z^2}\]

OpenStudy (loser66):

Let me try once :) z = f(x,y) , hence \(\dfrac{\partial f}{\partial y}\) means x is a constant. We have 4terms. Now the first term \((\sqrt 3\sqrt y)'= \sqrt 3 *y^{-2/3}\)

OpenStudy (michele_laino):

of course, we have: \[\large F\left( {x,y,z} \right) = \sqrt {3y} - y\cos \left( {xz} \right) - 2x + 3{z^2}=0\]

OpenStudy (khally92):

Ok makes sense.

OpenStudy (loser66):

Do the same with other terms. :)

OpenStudy (mathmale):

Wrap up: Find dz/dy, given \sqrt{3y} -ycos(xz)=2x-3z^2 by which you mean\[dz/dy,or z _{y}\]

OpenStudy (khally92):

@mathmale yayyy!!! its partial z partial y

OpenStudy (loser66):

the second term: \((-ycos(xz))' = -cos(xz) +ysin(xz)*x\dfrac{dz}{dy}\)

OpenStudy (mathmale):

given that given that\[given.that. \sqrt{3y} -ycos(xz)=2x-3z^2\]

OpenStudy (loser66):

the third term =0 the last term = \(-6z\dfrac{dz}{dy}\) put them on the original equation isolate \(dz/dy\), then you get the answer

OpenStudy (mathmale):

@loser66: Would we be better off using the partial differential operator|dw:1451072718819:dw|

OpenStudy (mathmale):

instead of that apostrophe? (-ycos(xz))' = -cos(xz) +ysin(xz)*x\dfrac{dz}{dy}

OpenStudy (michele_laino):

in more than one dimension, the final thesis, is: \[\large\frac{{\partial z}}{{\partial \left( {x,y} \right)}} = - {\left( {\frac{{\partial F}}{{\partial z}}\left( {x,y,z\left( {x,y} \right)} \right)} \right)^{ - 1}}\left( {\frac{{\partial F}}{{\partial \left( {x,y} \right)}}\left( {x,y,z\left( {x,y} \right)} \right)} \right)\]

OpenStudy (loser66):

I just "try once" . Not now whether it is right or wrong. :) rely on you guys to check it out.

OpenStudy (loser66):

*know

OpenStudy (khally92):

is loser on the right track, because as @Michele_Laino pointed out f(x y z)

OpenStudy (michele_laino):

where, by definition, we have: \[\Large\frac{{\partial z}}{{\partial \left( {x,y} \right)}} \equiv \left( {\frac{{\partial z}}{{\partial x}},\frac{{\partial z}}{{\partial y}}} \right)\]

OpenStudy (khally92):

kk @Loser66

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