

General OffTopic
Everything not about BMWs. Posts must be "primetime" safe and in good taste. You must be logged in to see subforums. Click here to browse all new posts. 

Thread Tools  Search this Thread  Rate Thread  Display Modes 
12112012, 08:56 AM  #141 
Registered User

I've seen about 4 methods taught on how to do partial fracs, 2 different ways in Calc2, 2 different ways in DiffEq and this last method I learned is uber easy.

12112012, 09:40 AM  #142 
drunken science

No worries. I just got done with the final and had to decompose 2 problems but my teacher was nice and both were polynomials that were easily factored so it was straightforward.
__________________

12112012, 10:02 AM  #143 
Registered User


12112012, 10:19 AM  #144 
drunken science

I had a great teacher and the stuff actually makes sense to me so that helps. She normally teaches linear algebra and PDE too but not next semester
__________________

12112012, 12:48 PM  #145  
Registered User

Quote:
PDE is typically a grad level course and not many people have to take it. Buddy of mine with a Ph.D in IE still has nightmares of PDE Most of the class passed, I'm fairly sure I will end up with a D Last edited by yousharenow; 12112012 at 12:49 PM. 

12152012, 09:38 AM  #146 
drunken science

2.5 points from an A, FML
__________________

12152012, 10:12 AM  #147 
Registered User
Join Date: Jun 2010
Location: BosniaHercegovina, New Jersey
Posts: 4,972
My Ride: SiennaE46 & Cbr600rr

lol i hated this class. Its deff one of the toughest ive taken.
__________________

12152012, 10:16 AM  #148 
Registered User
Join Date: Jul 2008
Location: Sunnyvale, CA < Ithaca, NY < dirty jerz (201) Useful Posts: 25
Posts: 136,482
My Ride: E46 332i,M3;E30 325i

:/
__________________
Kalim
(klx photo studio) M3 drive train conversion (S54 Swap, LSD, 6MT, suspension linkage)  UUC Stg 2 Organic Clutch  OEM MTech II Kit KW V2  BBS GT4 RE  Falken FK452  Alcon 6pot 365mm BBK  M3 steering wheel  Powerflex bushings 
01242013, 03:01 PM  #149 
drunken science

Doing some review for PDE and I got thrown a curveball. I'm not even sure where to begin with this one. I've tried starting with an auxiliary equation but how the fvck do you factor a 4th degree polynomial?
y''''+4y'''+6y''+4y+4=0
__________________

03032013, 10:06 PM  #150 
Registered User

Hey,
Can any of you guys help me real quick with this little Calc quiz I need to finish. I got problems 1,4 and 5 done, those were simple. Problem 2 and 3 are throwing me off. I don't really remember the theory rule for the high number derivatives like number 2. I'm sure this is really easy for some of you DE guys. lol Thanks
__________________
UUC Motorwerks  Vörsteiner  JLeviSW  VMR  DTMSpec  Euro Dyne  ModBargains  EAS Last edited by zuckuss00; 03032013 at 10:07 PM. 
03032013, 11:48 PM  #151 
Registered User

f(x)=x^(1/2)
f'(x)=(1/2)x^(3/2) f''(x)=(1/4)x^(5/2) continue that. I got F^(50)(x)=(1/1125899906842624)x^(101/2) #3 would suck to type
__________________
De gustibus non est disputandum. Last edited by Andy2108; 03042013 at 12:09 AM. 
03042013, 01:48 AM  #152 
Is not Persian
Join Date: Apr 2003
Location: Approximately La Crescenta, CA
Posts: 870
My Ride: '01 TiAg M3 Vert

^You did #2 wrong, the coefficient in front isn't right. For #2, let's look at the first 4 derivatives:
f(x)=x^{1/2} f'(x)=(1/2)x^{3/2} f''(x)=(3/4)x^{5/2} f'''(x)=(15/8)x^{7/2} f''''(x)=(105/16)x^{9/2} etc. So we have to come up with a way to figure out what f^{(a)}(x) is. First let's do the easy part, the negative/positive sign in front. It just changes every time, so we need a (1)^{a} in front f^{(a)}(x)=(1)^{a}... Then, we'll notice that in the denominator we have 2, 4, 8, 16, 32... so we need to put a (1/2)^{a} also f^{(a)}(x)=(1)^{a}(1/2)^{a}..... Simplifying: f^{(a)}(x)=(1/2)^{a}..... The numerator of the coefficient is a bit tricky, it's 1, 3, 15, 105.... but we know that this is just 1, 1*3, 1*3*5, 1*3*5*7.... so we have a hint that a factorial is needed. The second derivative has 1*3, the third has 1*3*5, the fourth has 1*3*5*7 etc so let's put (2a1)! in there. That will give us the right numbers, but we need to get rid of the evens, e.g. for the fourth derivative, (2a1)! will give you 1*2*3*4*5*6*7 but we need to get rid of the 2*4*6. You'll notice that 2*4*6 is just (1*2*3)*2*2*2, so if we take (2a1)! and divide it by 2^{(a1)}(a1)!, we should have the right coefficient. Let's add this whole part: f^{(a)}(x)=(1/2)^{a}(2a1)!/(2^{(a1)}(a1)!)..... Finally we need to get the power of x correct, we see that it's 3/2, 5/2, 7/2... so that's just (2a+1)/2. Let's add that in f^{(a)}(x)=(1/2)^{a}(2a1)!/(2^{(a1)}(a1)!)x^{(2a+1)/2} And that's the general formula for the ath derivative. Then just put 50 in place of the a's and you're done (I think the actual numbers are way too big to calculate with a calculator).
__________________
Last edited by my ass; Yesterday at 11:15 PM. Last edited by mash20; 03042013 at 01:49 AM. 
03042013, 02:07 AM  #153 
Registered User

your post was last edited before your post? impressive.
I totally overlooked that the coeficient in front was multipied by the exponent, which was changing for each derivitive. I just assumed it was (1/2) ^50 which made thing much more simple haha. I completely do not belong in this thread. ill just go ahead and show myself the way out now.
__________________
De gustibus non est disputandum. 
03042013, 02:09 AM  #154 
Is not Persian
Join Date: Apr 2003
Location: Approximately La Crescenta, CA
Posts: 870
My Ride: '01 TiAg M3 Vert

Oh come on, don't leave, there's plenty of room for everyone!
__________________
Last edited by my ass; Yesterday at 11:15 PM. 
03042013, 03:43 AM  #155  
Registered User

Quote:
I hate it when my professor throws us these curve ball questions that we hardly cover in class. I understand finding 2nd, 3rd and 4th derivatives, however anything past that begins to recur and basically you need to determine what derivative f(a) lands on. Any idea whats going on with the theory question #3?
__________________
UUC Motorwerks  Vörsteiner  JLeviSW  VMR  DTMSpec  Euro Dyne  ModBargains  EAS 

03042013, 07:11 AM  #156 
Is not Persian
Join Date: Apr 2003
Location: Approximately La Crescenta, CA
Posts: 870
My Ride: '01 TiAg M3 Vert

I was able to do #3, but it would be really hard to write it out here in a way that's understandable. Maybe I can write it out and take a picture...
__________________
Last edited by my ass; Yesterday at 11:15 PM. 
03042013, 07:25 AM  #157 
Is not Persian
Join Date: Apr 2003
Location: Approximately La Crescenta, CA
Posts: 870
My Ride: '01 TiAg M3 Vert

Ok, here it is. Let me know if you have any questions:
__________________
Last edited by my ass; Yesterday at 11:15 PM. 
03042013, 08:13 AM  #158 
drunken science

I just wanted to say good luck to anyone taking PDEs. Never have I been so interested in a class and had such little understanding of what was going on. It is by far the most interesting class I've taken, qualitatively, and the most difficult quantitatively.
__________________

03042013, 08:49 AM  #159 
Is not Persian
Join Date: Apr 2003
Location: Approximately La Crescenta, CA
Posts: 870
My Ride: '01 TiAg M3 Vert

I never actually took a PDE class, although many aspects of physics uses them. My favorite class by far was Complex Analysis. It was a little weird at times, but not too difficult, and it opens up a whole new realm when it comes to mathematics. Really interesting stuff, I highly recommend it!
__________________
Last edited by my ass; Yesterday at 11:15 PM. 
03042013, 08:58 AM  #160 
drunken science

But isn't QM mostly PDEs? There's an intro to it at the end of my PDE book. How did you manage to get through it?
I know there's a Real Analysis class offered and I've heard all the math majors bitching about that one; no one seems to enjoy it. I don't know if there is a complex analysis class offered or not. Topology is offered and I've heard good things about it, but I'm pretty sure I would have to go through Real Analysis in order to take it and I'm not sure I'm willing to risk my GPA to take a class I don't need. Plus, if I can't see how it applies to the real world then there's a better chance I'll get lost. That's pretty much how linear algebra is going, but luckily it's easy enough that I've given up trying to find a physical implication for all the theorems and just follow the rules to get the right answers.
__________________
Last edited by cowmoo32; 03042013 at 08:58 AM. 
Thread Tools  Search this Thread 
Display Modes  Rate This Thread 

