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# Cambridge Chat (previously New Cambridge Students Entry 2004) watch

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1. (Original post by Pollo Loco)
Please, stop posting these things. They confuse and frighten me, i can't cope with anything like that and i'm glad i don't have too. I'll start putting anatomy/pathology pics up if i keep seeing maths here, as a defence mechanism to stop me going mad.

DB

P.S. I'm not being serious in anyway. Carry on if you like but i'll be of no help at all
Mwahahahaha...

Shall I start posting java code and join the band wagon?
2. (Original post by xyro)
Try substituting r = sinh(x) . I don't know if I did it right, but it works (I hope).
ok doing that i get dr = (x^2+1)^(-1/2) dx

hence: (sinh^2 x + 1)^(-3/2) (x^2+1)^(-1/2) dx

where the hell do I go with that?
3. (Original post by Willa)
ok doing that i get dr = (x^2+1)^(-1/2) dx

hence: (sinh^2 x + 1)^(-3/2) (x^2+1)^(-1/2) dx

where the hell do I go with that?
That's a standard integral. So.. you go and look it up .

WOOOOOOOOOOOOOOOO! NUS cards are here! (not that I've not my hands on one yet, but according to the newsletter, we have the cards in some sort of storage facility).
4. Ok, let's see:

I (r^2+1)^(-3/2) dr ; r = sinh(x) => dr = cosh(x) dx

= I (sinh^2(x) + 1)^(-3/2) * cosh(x) dx

= I (cosh^2(x))^(-3/2) * cosh(x) dx

= I cosh^(-2)(x) dx

= tanh(x) + K = tanh(arcsinh(r)) + K

which can probably be simplified further.
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Or is there something wrong with the substitution step?
5. (Original post by xyro)
Dude/Part III mathmo, get a life! (Not that I'm complaining )
Think thats bad, I'm currently typing 3 out of the 4 courses I'm taking (GR has notes). One guy whose joined Part III from the US is taking 8 courses and typing them all up. He even does his answers to example sheets in Latex!!
(Original post by Camford)
but spend time with matrices just isn't my kind of thing . (although, I am developing a resentment towards programming too)
In my second year I had to write a C program to reduce a matrix to echelon form, and then use it to find the union and intersection of a group of given vectors.

Took me half of Christmas, about 600 lines of code, and after all that a spurious "1" kept appearing (seemingly at random) in one of the matrices. Took me about 3 days to find the error, which only needed me turning a 0 to a 1 in a "for" loop. By the end of it I was half nuts and having dreams about C code (well, closer to nightmares...)
6. (Original post by AlphaNumeric)
Took me half of Christmas, about 600 lines of code, and after all that a spurious "1" kept appearing (seemingly at random) in one of the matrices. Took me about 3 days to find the error, which only needed me turning a 0 to a 1 in a "for" loop. By the end of it I was half nuts and having dreams about C code (well, closer to nightmares...)
What did you use to program in C? 600 lines of code really shouldn't take you very long to write, then again, I'm a compsci. Suppose I know how to do the stuff you described, it probably takes me 3/4 days to write 600 lines and debug it. As for people like Alaric, they probably can do it in like... 4 hours?

I had to do a project over the summer. it end up just over 1k lines of code, took me quite a while to finish. Then again, I was going at a speed of 10 lines a day.
7. (Original post by Camford)
What did you use to program in C?
The C compiler the maths department provides.
(Original post by Camford)
Suppose I know how to do the stuff you described, it probably takes me 3/4 days to write 600 lines and debug it.
That included doing the project itself too. Writing gaussian elimination isn't a particularly quick thing to do either. I'd done programs which could plot phase plane solutions in under an hour, and since then I've done programs which plot the path of photons around black holes in under a day, but just thinking up a routine which can work for any matrix took a while. Its easy to do it for certain ones, but whatever routine I thought up would screw up if such and such entry was 0, or if the matrix that particular form. Once I have the mental image of the routine in my head, it takes a short while to get it into code, but the routines required were nasty. I probably could have curtailed the code somewhat and made it so it was specifically for the 5x6 matrices the project required, but I did it so that it worked for any nxm matric.
8. (Original post by AlphaNumeric)
The C compiler the maths department provides.
not the best thing to use when you want to find bugs in your program.

(Original post by AlphaNumeric)
That included doing the project itself too. Writing gaussian elimination isn't a particularly quick thing to do either. I'd done programs which could plot phase plane solutions in under an hour, and since then I've done programs which plot the path of photons around black holes in under a day, but just thinking up a routine which can work for any matrix took a while. Its easy to do it for certain ones, but whatever routine I thought up would screw up if such and such entry was 0, or if the matrix that particular form. Once I have the mental image of the routine in my head, it takes a short while to get it into code, but the routines required were nasty. I probably could have curtailed the code somewhat and made it so it was specifically for the 5x6 matrices the project required, but I did it so that it worked for any nxm matric.
Data Structures and Algorithms ought to teach me how deal with nasties like that... I would have gone with the easier option of getting a 3rd party C library that deals with matrices instead of writing all those things myself.
9. (Original post by Pollo Loco)
Please, stop posting these things. They confuse and frighten me, i can't cope with anything like that and i'm glad i don't have too. I'll start putting anatomy/pathology pics up if i keep seeing maths here, as a defence mechanism to stop me going mad.

DB

P.S. I'm not being serious in anyway. Carry on if you like but i'll be of no help at all

Mmmmmmm...have the mathmos/compscis/physicists of the world shut up yet?
10. So, what can anyone tell me about the complications of an anteroinferior dislocation of the glenohumeral joint?

So far, I have recurrence, fracture of the greater tuberosity of the humeral head, damage to the rotator cuff muscles and axillary nerve damage if the humeral head pushes inferriorly into the quadrangular space. The nerve damage can cause a loss of sensation on the laterar aspect of the shoulder and paralyisis of the deltoid. Anything else?
11. (Original post by Camford)
What did you use to program in C? 600 lines of code really shouldn't take you very long to write, then again, I'm a compsci. Suppose I know how to do the stuff you described, it probably takes me 3/4 days to write 600 lines and debug it. As for people like Alaric, they probably can do it in like... 4 hours?
In C I seem to be able to do about 300-500 lines a day of debugged and commented code, and that seems fairly normal for the class. The variation comes from how well defined the specification is and the caffeine levels available.

A.
12. (Original post by Camford)
I would have gone with the easier option of getting a 3rd party C library that deals with matrices instead of writing all those things myself.
The C compiler the maths department provides does matrices, the whole point of the project was the write a program to do it yourself.
If I remember correctly, at the end of the project you could use the inbuilt routine to check you were right...
(Original post by Alaric)
and the caffeine levels available.
Some of my best coding is done in the middle of the night with the aid of stimulants and lack of food and sleep.

Makes you go a little weird when you've been sleeping during the day and coding during the night for 3 or 4 days in a row though...
13. (Original post by AlphaNumeric)
Some of my best coding is done in the middle of the night with the aid of stimulants and lack of food and sleep.

Makes you go a little weird when you've been sleeping during the day and coding during the night for 3 or 4 days in a row though...
Although I generally don't use coffee or anything like that.
14. (Original post by AlphaNumeric)
Some of my best coding is done in the middle of the night with the aid of stimulants and lack of food and sleep.

Makes you go a little weird when you've been sleeping during the day and coding during the night for 3 or 4 days in a row though...
I think I code best in the late afternoon now. I used to be a middle of the night person but from my performance when I've pulled a couple of 16hour days recently, I get a lot worse after 9pm.

The good thing about where I work is the unlimited free caffeine and snacks, really necessary to keep me going when they require one to be in at 8am.

A.
15. (Original post by Alaric)
I think I code best in the late afternoon now. I used to be a middle of the night person but from my performance when I've pulled a couple of 16hour days recently, I get a lot worse after 9pm.

The good thing about where I work is the unlimited free caffeine and snacks, really necessary to keep me going when they require one to be in at 8am.

A.
16 hour days?!! NOOOOOOOOOOOOOOOOOO
16. (Original post by Alaric)
The good thing about where I work is the unlimited free caffeine and snacks, really necessary to keep me going when they require one to be in at 8am. .
In Febuary I was browsing around and came across a website selling caffeine for £5. Not the usual "96 Pro plus caffeine tablets (4.8g)" you can buy in Superdrug, but 400g in powder form!

So I thought "£5?! **** it, I'll buy some!" I've still got the VAST majority of it left, and I'll probably still have the majority left when I finish the PhD I want to do! (I'm doing Part III ATM).
17. Pure caffeine?!!
18. How wired do you get? Do you recommend trying to get hold of some?
19. He he he! I saw Helenia dancing last night at the bop wearing a bin bag. Don't see that every day...
20. (Original post by Camford)
16 hour days?!! NOOOOOOOOOOOOOOOOOO
Hehe, it's still only training, unless there's a major problem with one of the systems it's apparently unlikely that i'll be doing that kind of hours when I'm done and a proper worker. There's not been many anyway, normally it's only 9 or 10.

A.
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(Original post by AlphaNumeric)
In Febuary I was browsing around and came across a website selling caffeine for £5. Not the usual "96 Pro plus caffeine tablets (4.8g)" you can buy in Superdrug, but 400g in powder form!

So I thought "£5?! **** it, I'll buy some!" I've still got the VAST majority of it left, and I'll probably still have the majority left when I finish the PhD I want to do! (I'm doing Part III ATM).
**** that's extreme, careful not to die with that quantity!

A.

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Updated: June 24, 2006
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