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1018
 one year ago
please help. numbers 24 & 25 (picture)
1018
 one year ago
please help. numbers 24 & 25 (picture)

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madhu.mukherjee.946
 one year ago
Best ResponseYou've already chosen the best response.0@ganeshie8

1018
 one year ago
Best ResponseYou've already chosen the best response.0oh and i tried to answer #23 but my answer didnt show up among the choices. if anyone can answer that would be helpful too. thanks!

welshfella
 one year ago
Best ResponseYou've already chosen the best response.5dw:1441468653415:dw

welshfella
 one year ago
Best ResponseYou've already chosen the best response.5dw:1441468744582:dw

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1Shouldn't the integrand be \(2\pi\ x^2 dx\) ?

welshfella
 one year ago
Best ResponseYou've already chosen the best response.5no the area of a 'slice' is pi r^2

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1Sorry meant \(2\pi\ (x^2)^2 dx \)

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1Area of a circle, lol

welshfella
 one year ago
Best ResponseYou've already chosen the best response.5 i dont think so  why the 2 ?

welshfella
 one year ago
Best ResponseYou've already chosen the best response.5no that is not the curve the curve is y  x^2

welshfella
 one year ago
Best ResponseYou've already chosen the best response.5dw:1441469338036:dw

welshfella
 one year ago
Best ResponseYou've already chosen the best response.5we only dealing with x = 0 to x = 1

welshfella
 one year ago
Best ResponseYou've already chosen the best response.5dw:1441469432075:dw

welshfella
 one year ago
Best ResponseYou've already chosen the best response.5it is the sum of all the discs with height dx and radius x^2

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1Anyway, for 24 and 25 use the definition of the total differential: for z = f(x,y) \[dz = \frac{\partial f }{\partial x} dx + \frac{\partial f }{\partial y} dy\]

welshfella
 one year ago
Best ResponseYou've already chosen the best response.5the cross section is a circle

welshfella
 one year ago
Best ResponseYou've already chosen the best response.5partial differentials

1018
 one year ago
Best ResponseYou've already chosen the best response.0hey guys! sorry i lost my connection

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1@welshfella got the answer for 23 in his first two posts. You can ignore the discussion under that. For 24 and 25 use \[dz = \frac{\partial f }{\partial x} dx + \frac{\partial f }{\partial y} dy\]

1018
 one year ago
Best ResponseYou've already chosen the best response.0oh yes! squared. i forgot x^2 still needs ^2. thanks @welshfella thanks @beginnersmind

1018
 one year ago
Best ResponseYou've already chosen the best response.0ok ill try and see if i can get the answer

1018
 one year ago
Best ResponseYou've already chosen the best response.0@beginnersmind hey can you show me your work, i think im close to it but i dont fully understand. thanks

1018
 one year ago
Best ResponseYou've already chosen the best response.0i mean when im deriving already. i think im missing something

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1You mean show why my formula is true? Or apply it?

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1ok, for 24 dw:1441470707423:dw

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1Remember to take the partial derivative with respect to x you just treat y as a constant.

1018
 one year ago
Best ResponseYou've already chosen the best response.0oh i should still write the dx and dy in my answer?

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1Sure, they are asking for dz. The answer will be in a form: (something) * dx + (something else) * dy

1018
 one year ago
Best ResponseYou've already chosen the best response.0ok thanks! Ill try the other one thanks again!

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1No problem. Let me know if you want me to check your solution.

1018
 one year ago
Best ResponseYou've already chosen the best response.0oh no wait can you help me out on 25, hahaha. that is a hard one

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1Oh, 25 is different because x and y are a function of t.

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1Ok, it's actually simpler than 24

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1They are only asking for dx/dt. You can ignore everything except the definition of x(t).

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1It's weird though, I'm getting \( \pi/2\), for 25. Paging @welshfella

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1pi/2 that is. But it's not one of the options.

1018
 one year ago
Best ResponseYou've already chosen the best response.0do i just ignore the e? i will just derive the exponent then sub to the orig value?

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1IDK, I checked my work and I'm still getting pi/2 Here it is in full if someone wants to go over it. x(t) = t*cost dx/dt = cost  t*sint evaluate at t=pi/2 dx/dt = 0  (pi/2)*1 = pi/2.

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1@ganeshie8 can you check please?

1018
 one year ago
Best ResponseYou've already chosen the best response.0that's my sol'n for x. haha at least i'm getting somewhere

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1The only thing I can think of is that they actually meant to ask for dz/dt and dx/dt is a typo.

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1I tried calculating dz/dt for t = pi/2 and got [(pi)^3]/8. I think I'll just have to give up here. Something looks fishy, especially giving z(x(t),y(t)) but then only asking for dx/dt.

1018
 one year ago
Best ResponseYou've already chosen the best response.0maybe there really is an error, hey thanks anyway. big help!

beginnersmind
 one year ago
Best ResponseYou've already chosen the best response.1No problem. Just for completeness's sake this is the formula for dz/dtdw:1441473257074:dw
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