Recent content by gamma-ray-burst

Oh wow you guys are amazing. Thanks a lot for all the answers! Yet again, I was complicating things for nothing. I know that next week we will see indeterminations of forms like "0/0" and "inf/inf" and things like that and I was afraid that "#/0" was some special case where I had to do other...

hey hi. i'm just starting differentials and now we are seeing the limits. i have a question. there is one example that goes like this : lim 4 / (x²+2x+1) x--> -1 well with simple calculations using -1(-) and -1(+), i know that the answer is infinity. plus, if i trace the graph...

engineers can demolish forty beers. they are the guys who apply science to everyday life, to make it easier. i'm currently studying civil engineering. talking to people from other faculties, it's always funny to see how civil engineers are the one working for the people who has no money : you...

well it's been a while since i read about this stuff, but i'd say that the main problem with singularities was actually the fact that we had to say that there was "infinite" stuff going on down there. one of the points of string theory is to say that there is no infinitely small dimension, so...

Well I know. It's easy to find the partial derivatives when we have the function. That I can find. But as I said, we have just done one example with the "definition", so I quite don't see how. It's like d[df/dx]/dx When you derivate the function you just assume y as constant. But when it comes...

Homework Statement We are given a table where showing the points x and y and values of a function f(x,y). The function itself is not given. I have to find the partial derivatives f'x, f'y, f''xx, f''yy and f''xy around the point (2,3). Homework Equations I have to use the definition ...

And wouldn't dy/du = 1 because they are independent or something? f(2u, u-3v) Or I'm talking crap. oyoyoy

Ok so now I have : d²f/dx² = d/dx [ 1/2 (df/du) + 1/6 (df/dv) ] Is this right? Damn I feel so stupid because I feel that it's not that hard :( I'm not even sure about the next steps. I think I need a drink.

And there was light. Wow thanks now that's clear :D So now I just have to find d²f/dx² = d/dx [(df/du)(du/dx) + (df/dv)(dv/dx)] (or I'm not sure, got to check my notes about composed functions) and rewrite the equation with the new values found? Like "what I'm about to find" + -1/3 (df/dv) = 0 ...

Ok now, sorry I was fooling around with the other numbers of the homework. So should I do something like, assuming f = f(x,y), : df/du = (df/dx)(dx/du) + (df/dy)(dy/du) and df/dv = (df/dx)(dx/dv) + (df/dy)(dy/dv) But then what does it means to transform the equation into the coordinates system...

Hey hmm, the partial derivative in x of "e^(xy)", is it zero?

Oooh yes, that definitely rings a bell. I'll try that tonight, thanks :D

Homework Statement f(x,y) a function of two variables. x = 2u y = u-3v Using a change of variables, transform the equation (d²f/dx²) + (df/dy) = 0 into the coordinates system {u,v}.Homework Equations We have kind of a replacement teacher for the session and it is his first time giving the...