Help & FAQs    Search BCF    Members    Groups    Events Calendar
Resend my activation email : Register : Log in 
BCF: Bike Chat Forums


Maths guru's ..... help needed

 Reply to topic
Bike Chat Forums Index -> Random Banter Goto page 1, 2  Next
View previous topic : View next topic  
Author Message

Nick 50
World Chat Champion



Joined: 24 Jul 2011
Karma :
PostPosted: 11:01 - 15 Dec 2012    Post subject: Maths guru's ..... help needed Reply with quote
So i'm wondering if anyone can help with a problem i'm stuck with.

It's a Partial Differentiation problem and finding Stationary Points.

The problem:

https://i300.photobucket.com/albums/nn6/ElScampio/Maths_zps74166d91.jpg

As you can see, partially differentiating is no problem. I set both equations to 0.

The problems is now doing the maths where I have a singular value for either x or y which I can put back into the equations to solve for the other variable.
No matter which route I go down, I don't get anywhere near the answer.

Anyone any ideas?
____________________
Current Bikes: ZX7r 97 (Black Beauty), VFR400 NC24 (The banana)
Previous Bikes: Aprilia Tuono 03 (The Beast), CBR600f (97)
First bike: A GZ125 Lemon.......
 Back to top
View user's profile Send private message You must be logged in to rate posts

Tungtvann
World Chat Champion



Joined: 07 Dec 2012
Karma :
PostPosted: 11:13 - 15 Dec 2012    Post subject: Reply with quote
Yeah, gimme a sec. Just going to get a pencil and some paper...
 Back to top
View user's profile Send private message You must be logged in to rate posts

Nick 50
World Chat Champion



Joined: 24 Jul 2011
Karma :
PostPosted: 11:25 - 15 Dec 2012    Post subject: Reply with quote
Tungtvann wrote:
Yeah, gimme a sec. Just going to get a pencil and some paper...


Thanks and good luck........... you may need it. It has had quite a few people at Uni baffled. Laughing
____________________
Current Bikes: ZX7r 97 (Black Beauty), VFR400 NC24 (The banana)
Previous Bikes: Aprilia Tuono 03 (The Beast), CBR600f (97)
First bike: A GZ125 Lemon.......
 Back to top
View user's profile Send private message You must be logged in to rate posts

swampy
World Chat Champion



Joined: 04 Aug 2004
Karma :
PostPosted: 11:27 - 15 Dec 2012    Post subject: Reply with quote
Clearly the answer is potato hth.
____________________
"I hate to advocate drugs, alcohol, violence or insanity to anyone, but they've always worked for me." Hunter S Thompson
"Faster, faster, faster, until the thrill of speed overcomes the fear of death..." Hunter S Thompson
 Back to top
View user's profile Send private message Send e-mail You must be logged in to rate posts

MCW
World Chat Champion



Joined: 20 Aug 2012
Karma :
PostPosted: 12:15 - 15 Dec 2012    Post subject: Reply with quote
Sorry to sound like my mother, but isn't the point of being set these questions for you to work out the answers, and thus learn something as you go?
 Back to top
View user's profile Send private message You must be logged in to rate posts

Im-a-Ridah
World Chat Champion



Joined: 20 Oct 2006
Karma :
PostPosted: 12:17 - 15 Dec 2012    Post subject: Reply with quote
Be interesting to see the results...

but computers FTW.
 Back to top
View user's profile Send private message Send e-mail You must be logged in to rate posts

hellkat
Super Spammer



Joined: 12 Jul 2004
Karma :
PostPosted: 12:22 - 15 Dec 2012    Post subject: Reply with quote
MCW wrote:
Sorry to sound like my mother, but isn't the point of being set these questions for you to work out the answers, and thus learn something as you go?

But we're waiting for someone brainy to come along and tell us the answer AND how they achieved that answer.

I agree with swampy.
The answer is potato.

And my reason for that is that (everybody knows that) the back-to-front-6 is secret code for "This question looks complicated, but means nothing except for 'How much wood can a woodchuck chuck if a woodchuck could chuck wood?'"

... and of course the answer to that is ALWAYS "potato".
____________________
Not nearly as interesting in real life.
 Back to top
View user's profile Send private message Send e-mail You must be logged in to rate posts

MCW
World Chat Champion



Joined: 20 Aug 2012
Karma :
PostPosted: 12:24 - 15 Dec 2012    Post subject: Reply with quote
hellkat wrote:
But we're waiting for someone brainy to come along and tell us the answer AND how they achieved that answer.

I'll have a look at it later...
 Back to top
View user's profile Send private message You must be logged in to rate posts

Im-a-Ridah
World Chat Champion



Joined: 20 Oct 2006
Karma :
PostPosted: 12:28 - 15 Dec 2012    Post subject: Reply with quote
Have you tried...

https://www.google.com/search?q=partial+differentiation+stationary+points
 Back to top
View user's profile Send private message Send e-mail You must be logged in to rate posts

Nick 50
World Chat Champion



Joined: 24 Jul 2011
Karma :
PostPosted: 12:31 - 15 Dec 2012    Post subject: Reply with quote
MCW wrote:
Sorry to sound like my mother, but isn't the point of being set these questions for you to work out the answers, and thus learn something as you go?


I agree in theory.

This is of an revision sheet for exams I have in Jan. They do give answers to some of the questions. The idea of giving the answers is so you know you are doing it correctly and thus build up your confidence in what you are doing.
I'm only in the 1st year and the Maths part is vitally important for setting the underlying knowledge for the rest of the course. So I guess they do try and help so you understand as much as possible before we get hit with the complicated stuff in future years.

Im-a-Ridah wrote:
Have you tried...

https://www.google.com/search?q=partial+differentiation+stationary+points


I know the process for doing it and can happily do it for less complicated functions. This one though is seriously tough. Unfortunately no matter how much I try, my algebraic manipulation skills aren't good enough Crying or Very sad
____________________
Current Bikes: ZX7r 97 (Black Beauty), VFR400 NC24 (The banana)
Previous Bikes: Aprilia Tuono 03 (The Beast), CBR600f (97)
First bike: A GZ125 Lemon.......
 Back to top
View user's profile Send private message You must be logged in to rate posts

Im-a-Ridah
World Chat Champion



Joined: 20 Oct 2006
Karma :
PostPosted: 13:30 - 15 Dec 2012    Post subject: Reply with quote
Nick 50 wrote:
MCW wrote:
Sorry to sound like my mother, but isn't the point of being set these questions for you to work out the answers, and thus learn something as you go?


I agree in theory.

This is of an revision sheet for exams I have in Jan. They do give answers to some of the questions. The idea of giving the answers is so you know you are doing it correctly and thus build up your confidence in what you are doing.
I'm only in the 1st year and the Maths part is vitally important for setting the underlying knowledge for the rest of the course. So I guess they do try and help so you understand as much as possible before we get hit with the complicated stuff in future years.

Im-a-Ridah wrote:
Have you tried...

https://www.google.com/search?q=partial+differentiation+stationary+points


I know the process for doing it and can happily do it for less complicated functions. This one though is seriously tough. Unfortunately no matter how much I try, my algebraic manipulation skills aren't good enough Crying or Very sad


Are you studying maths?
 Back to top
View user's profile Send private message Send e-mail You must be logged in to rate posts

Skudd
Super Spammer



Joined: 01 Oct 2006
Karma :
PostPosted: 13:36 - 15 Dec 2012    Post subject: Reply with quote
Just out of interest, what would you use this for and why. It used to cheese me off that when I was doing maths at school all those years ago, the tutors couldn't put things into real world situations, but since then I have come across load of things that the maths would have helped with, you have to remember though that I come from a time when we had to look up cos, tan, sin in a little book and no calculators were permitted.
____________________
Famous last words of Humpty Dumpty. " Stop pushing me "
Petty Anarchists look at "1984".............. The Visionary looks at "Animal Farm".
 Back to top
View user's profile Send private message Send e-mail You must be logged in to rate posts

Pete.
Super Spammer



Joined: 22 Aug 2006
Karma :
PostPosted: 13:39 - 15 Dec 2012    Post subject: Reply with quote
Quote:
Just out of interest, what would you use this for and why.


Helping out pretty maths students with a view to getting your nuts in?
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy
 Back to top
View user's profile Send private message Visit poster's website You must be logged in to rate posts

Nick 50
World Chat Champion



Joined: 24 Jul 2011
Karma :
PostPosted: 13:43 - 15 Dec 2012    Post subject: Reply with quote
Im-a-Ridah wrote:


Are you studying maths?


Thankfully not, i'm studying Mechanical Engineering.

Skudd wrote:
Just out of interest, what would you use this for and why. It used to cheese me off that when I was doing maths at school all those years ago, the tutors couldn't put things into real world situations, but since then I have come across load of things that the maths would have helped with, you have to remember though that I come from a time when we had to look up cos, tan, sin in a little book and no calculators were permitted.


Laughing I will try my best to explain in the limited knowledge I have.

Partial Differentiation is used when you have normally 2 independent variables in a a equation.

An analogy of sorts is Power of a bike engine. The Power depends on lots of differing things which can change independently of the others, e.g fuel mixture, revs used, temperature etc etc.

Partial differentiation allows you to analyse how Power output would change if you affected one of the input factors. It allows you to say "Well if I hold all the variables constant except for the fuel mixture, what would happen to the power output if I changed it?". Then you could hold fuel mixture constant and then change the revs and see how that will affect the Power etc etc.

Stationary Points allow you to identify when no change occurs. So if you anaylsed say changing the fuel mixture and differing the revs, is there any point on the power curve where there is no increase (a flat spot of sort)?

The link below explains it (probably better than I have) using hills:

https://www2.imperial.ac.uk/metric/metric_public/partial_differentiation/applications/stationary_points.html

In Engineering, many many things will have more than 1 thing changing. So Partial Differentiation is a "biggy" thing to understand.

Hope that makes some sense.
____________________
Current Bikes: ZX7r 97 (Black Beauty), VFR400 NC24 (The banana)
Previous Bikes: Aprilia Tuono 03 (The Beast), CBR600f (97)
First bike: A GZ125 Lemon.......

Last edited by Nick 50 on 13:57 - 15 Dec 2012; edited 2 times in total
 Back to top
View user's profile Send private message You must be logged in to rate posts

noobRider
World Chat Champion



Joined: 23 Sep 2012
Karma :
PostPosted: 13:48 - 15 Dec 2012    Post subject: Reply with quote
Does this help?

Also Monkey Saddles ...

or this
____________________
Licence: Nov 2012, Bikes: Suzuki GN125, Moto Guzzi Strada 750, Triumph Sprint ST 955i x 2
AnPhonEh: I need plans, I need contingency plans also, I need back up contingency plans
 Back to top
View user's profile Send private message You must be logged in to rate posts

Lurkio
L Plate Warrior



Joined: 15 Dec 2012
Karma :
PostPosted: 13:52 - 15 Dec 2012    Post subject: Reply with quote
Use the first equation to find y in terms of x. Plug this into the second. Rearrange to find a quartic. NB x^4 = (x^2)^2
 Back to top
View user's profile Send private message You must be logged in to rate posts

lihp
World Chat Champion



Joined: 22 Sep 2010
Karma :
PostPosted: 13:56 - 15 Dec 2012    Post subject: Reply with quote
Nick 50 wrote:


Thankfully not, i'm studying Mechanical Engineering.


Balls, I start my Mech Engineering in Feb, now I have that to look forward to Sad
 Back to top
View user's profile Send private message You must be logged in to rate posts

Nick 50
World Chat Champion



Joined: 24 Jul 2011
Karma :
PostPosted: 14:01 - 15 Dec 2012    Post subject: Reply with quote
noobRider wrote:
Does this help?

Also Monkey Saddles ...

or this


Thumbs Up

I fired it into Wolfram Alpha and it helps in show where the max,min and saddle points are on the plot.
Unfortunately it doesn't explain how they got the answer Crying or Very sad

Lurkio wrote:
Use the first equation to find y in terms of x. Plug this into the second. Rearrange to find a quartic. NB x^4 = (x^2)^2


Yep, I know the process of doing it and can do it with simpler functions. It's just this function is pretty tough and i've struggled getting from equation to 0, to getting to the stationary point co-ordinates.

PhilDawson8270 wrote:


Balls, I start my Mech Engineering in Feb, now I have that to look forward to Sad


Good choice.

What you level are you studying and where at?

There are few on here that have Engineering degrees or currently doing it, so if you have an issue, this is a good place to start.

But as you've guessed, Mech Engineering is very heavy in Maths.
____________________
Current Bikes: ZX7r 97 (Black Beauty), VFR400 NC24 (The banana)
Previous Bikes: Aprilia Tuono 03 (The Beast), CBR600f (97)
First bike: A GZ125 Lemon.......
 Back to top
View user's profile Send private message You must be logged in to rate posts

T0MMY
World Chat Champion



Joined: 08 Jun 2008
Karma :
PostPosted: 14:06 - 15 Dec 2012    Post subject: Reply with quote
Pete. wrote:

Helping out pretty maths students with a view to getting your nuts in?


Good luck with that Laughing
____________________
ZX6R + CBR600RR
 Back to top
View user's profile Send private message You must be logged in to rate posts

lihp
World Chat Champion



Joined: 22 Sep 2010
Karma :
PostPosted: 14:17 - 15 Dec 2012    Post subject: Reply with quote
Nick 50 wrote:


Good choice.

What you level are you studying and where at?


Bachelors, though it's mechanical engineering design, but core modules will more than likely be similar, studying with open university as I still need to stay in full time work Sad I have been working in engineering for years, but maths will be a struggle initially!
 Back to top
View user's profile Send private message You must be logged in to rate posts

Lurkio
L Plate Warrior



Joined: 15 Dec 2012
Karma :
PostPosted: 14:19 - 15 Dec 2012    Post subject: Reply with quote
3x^2 + 2xy - 4 = 0 gives y = (4 - 3x^2)/2x

Stop telling yourself this is difficult and just do it.
 Back to top
View user's profile Send private message You must be logged in to rate posts

Pete.
Super Spammer



Joined: 22 Aug 2006
Karma :
PostPosted: 15:16 - 15 Dec 2012    Post subject: Reply with quote
T0MMY wrote:
Pete. wrote:

Helping out pretty maths students with a view to getting your nuts in?


Good luck with that Laughing


https://en.wikipedia.org/wiki/Rachel_Riley

Smile
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy
 Back to top
View user's profile Send private message Visit poster's website You must be logged in to rate posts

Skudd
Super Spammer



Joined: 01 Oct 2006
Karma :
PostPosted: 15:21 - 15 Dec 2012    Post subject: Reply with quote
Nick 50 wrote:
Im-a-Ridah wrote:


Are you studying maths?


Thankfully not, i'm studying Mechanical Engineering.

Skudd wrote:
Just out of interest, what would you use this for and why. It used to cheese me off that when I was doing maths at school all those years ago, the tutors couldn't put things into real world situations, but since then I have come across load of things that the maths would have helped with, you have to remember though that I come from a time when we had to look up cos, tan, sin in a little book and no calculators were permitted.


Laughing I will try my best to explain in the limited knowledge I have.

Partial Differentiation is used when you have normally 2 independent variables in a a equation.

An analogy of sorts is Power of a bike engine. The Power depends on lots of differing things which can change independently of the others, e.g fuel mixture, revs used, temperature etc etc.

Partial differentiation allows you to analyse how Power output would change if you affected one of the input factors. It allows you to say "Well if I hold all the variables constant except for the fuel mixture, what would happen to the power output if I changed it?". Then you could hold fuel mixture constant and then change the revs and see how that will affect the Power etc etc.

Stationary Points allow you to identify when no change occurs. So if you anaylsed say changing the fuel mixture and differing the revs, is there any point on the power curve where there is no increase (a flat spot of sort)?

The link below explains it (probably better than I have) using hills:

https://www2.imperial.ac.uk/metric/metric_public/partial_differentiation/applications/stationary_points.html

In Engineering, many many things will have more than 1 thing changing. So Partial Differentiation is a "biggy" thing to understand.

Hope that makes some sense.


Thumbs Up I get it.
____________________
Famous last words of Humpty Dumpty. " Stop pushing me "
Petty Anarchists look at "1984".............. The Visionary looks at "Animal Farm".
 Back to top
View user's profile Send private message Send e-mail You must be logged in to rate posts

swampy
World Chat Champion



Joined: 04 Aug 2004
Karma :
PostPosted: 15:39 - 15 Dec 2012    Post subject: Reply with quote
hellkat wrote:
MCW wrote:
Sorry to sound like my mother, but isn't the point of being set these questions for you to work out the answers, and thus learn something as you go?

But we're waiting for someone brainy to come along and tell us the answer AND how they achieved that answer.

I agree with swampy.
The answer is potato.

And my reason for that is that (everybody knows that) the back-to-front-6 is secret code for "This question looks complicated, but means nothing except for 'How much wood can a woodchuck chuck if a woodchuck could chuck wood?'"

... and of course the answer to that is ALWAYS "potato".


Ahh yes, King Edwards theorem.... Very pertinent in this case...
____________________
"I hate to advocate drugs, alcohol, violence or insanity to anyone, but they've always worked for me." Hunter S Thompson
"Faster, faster, faster, until the thrill of speed overcomes the fear of death..." Hunter S Thompson
 Back to top
View user's profile Send private message Send e-mail You must be logged in to rate posts

T0MMY
World Chat Champion



Joined: 08 Jun 2008
Karma :
PostPosted: 16:00 - 15 Dec 2012    Post subject: Reply with quote
Pete. wrote:

https://en.wikipedia.org/wiki/Rachel_Riley

Smile


https://www.thesundaytimes.co.uk/sto/multimedia/dynamic/00305/STR11WIN01_305195k.jpg

https://i1.ytimg.com/vi/p-16uZCXZfw/hqdefault.jpg

I stand corrected Laughing
____________________
ZX6R + CBR600RR
 Back to top
View user's profile Send private message You must be logged in to rate posts
Old Thread Alert!

The last post was made 13 years, 63 days ago. Instead of replying here, would creating a new thread be more useful?
  Display posts from previous:   
This page may contain affiliate links, which means we may earn a small commission if a visitor clicks through and makes a purchase. By clicking on an affiliate link, you accept that third-party cookies will be set.

Post new topic   Reply to topic    Bike Chat Forums Index -> Random Banter All times are GMT
Goto page 1, 2  Next
Page 1 of 2

 
 You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum

Read the Terms of Use! - Powered by phpBB © phpBB Group
 
Debug Mode: ON - Server: birks (www) - Page Generation Time: 0.10 Sec - Server Load: 0.36 - MySQL Queries: 13 - Page Size: 137.87 Kb