Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Foo Off-Topic chit chat with no general subject.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 05-21-07, 02:45 PM   #1
ManBearPig
1/2 man,1/2 bear,1/2 pig
Thread Starter
 
ManBearPig's Avatar
 
Join Date: May 2004
Location: .
Bikes: .
Posts: 1,122
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Math Majors -- simplify this

If you can, please simplify this expression:

SQRT(X^2 + Y^2) * COS(45 - ATAN(Y/X))



The expression in the COS( ) looks familiar to me, but it has been 10 years since I finished my engineering degree. Thanks!
__________________
...
ManBearPig is offline   Reply With Quote
Old 05-21-07, 02:47 PM   #2
Taerom
Hazardous
 
Taerom's Avatar
 
Join Date: Jun 2005
Location: Quarantine
Bikes: 2005 Trek Liquid 55, 2009 Haro Mary SS
Posts: 727
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
42
Taerom is offline   Reply With Quote
Old 05-21-07, 02:50 PM   #3
jsharr
You Know!? For Kids!
 
jsharr's Avatar
 
Join Date: Apr 2005
Location: Just NW of Richardson Bike Mart
Bikes: '05 Trek 1200 / '90 Trek 8000 / '? Falcon Europa
Posts: 6,157
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Quote:
Originally Posted by Towlie
If you can, please simplify this expression:

SATAN



The expression in the COS( ) looks familiar to me, but it has been 10 years since I finished my engineering degree. Thanks!
I removed all the unnecesasry stuff and got the answer to your math problem
__________________
Are you a registered member? Why not? Click here to register. It's free and only takes 27 seconds! Help out the forums, abide by our community guidelines.
Quote:
Originally Posted by colorider View Post
Phobias are for irrational fears. Fear of junk ripping badgers is perfectly rational. Those things are nasty.
jsharr is offline   Reply With Quote
Old 05-21-07, 02:51 PM   #4
ManBearPig
1/2 man,1/2 bear,1/2 pig
Thread Starter
 
ManBearPig's Avatar
 
Join Date: May 2004
Location: .
Bikes: .
Posts: 1,122
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Please, express the answer in terms of X and Y only; no supernatural deities.
__________________
...
ManBearPig is offline   Reply With Quote
Old 05-21-07, 02:52 PM   #5
x136 
phony collective progress
 
x136's Avatar
 
Join Date: Sep 2006
Location: San Hoosey
Bikes: http://velospace.org/user/36663
Posts: 2,981
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Who is this Y? Is she hot?
__________________
x136 is offline   Reply With Quote
Old 05-21-07, 02:58 PM   #6
KingTermite 
On my TARDIScycle!
 
KingTermite's Avatar
 
Join Date: Jun 2005
Location: Eastside Seattlite Termite Mound
Bikes: Trek 520, Trek Navigator 300, Peugeot Versailles PE10DE
Posts: 3,924
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Taerom
42
+1


Do your own math homework.
__________________
Quote:
Originally Posted by coffeecake View Post
- it's pretty well established that Hitler was an *******.
KingTermite is offline   Reply With Quote
Old 05-21-07, 03:09 PM   #7
ManBearPig
1/2 man,1/2 bear,1/2 pig
Thread Starter
 
ManBearPig's Avatar
 
Join Date: May 2004
Location: .
Bikes: .
Posts: 1,122
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
This ain't homework. The question is directed to math majors, not math phobics. This is not an advanced problem in the grand scheme of things; I am simply rusty on my trig and algebra.
__________________
...
ManBearPig is offline   Reply With Quote
Old 05-21-07, 03:13 PM   #8
scrapmetal
Senior Member
 
scrapmetal's Avatar
 
Join Date: Jun 2006
Location: Quartered safe out here
Bikes: 197x?? Raleigh rescued from scrap metal; Specialized Roubaix
Posts: 382
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Taerom
42
what else ..... and thanks for the fish.
scrapmetal is offline   Reply With Quote
Old 05-21-07, 03:16 PM   #9
KingTermite 
On my TARDIScycle!
 
KingTermite's Avatar
 
Join Date: Jun 2005
Location: Eastside Seattlite Termite Mound
Bikes: Trek 520, Trek Navigator 300, Peugeot Versailles PE10DE
Posts: 3,924
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Towlie
This ain't homework. The question is directed to math majors, not math phobics. This is not an advanced problem in the grand scheme of things; I am simply rusty on my trig and algebra.
No it's not advanced....never said it was. I'm not a math phobic by ANY stretch of the definition (I have a bachelors and masters degree in computer engineering...methinks I've taken some math courses).....I still think it looks like you are trying to get help with a homework problem.
__________________
Quote:
Originally Posted by coffeecake View Post
- it's pretty well established that Hitler was an *******.
KingTermite is offline   Reply With Quote
Old 05-21-07, 03:31 PM   #10
ManBearPig
1/2 man,1/2 bear,1/2 pig
Thread Starter
 
ManBearPig's Avatar
 
Join Date: May 2004
Location: .
Bikes: .
Posts: 1,122
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I am 33 yrs old; I am not doing homework; I am a BSME (UT Austin, May, 1997)....I derived this expression trigonometrically on a project I am working on, and I don't know/remember how to simplify it.

I don't remember all the trigonometric identities because I haven't worked with them for a long while, e.g.

http://www.sosmath.com/trig/Trig5/trig5/trig5.html
__________________
...
ManBearPig is offline   Reply With Quote
Old 05-21-07, 03:40 PM   #11
CdCf
Videre non videri
 
Join Date: Sep 2004
Location: Gothenburg, Sweden
Bikes: 1 road bike (simple, light), 1 TT bike (could be more aero, could be lighter), 1 all-weather commuter and winter bike, 1 Monark 828E ergometer indoor bike
Posts: 3,208
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by KingTermite
Quote:
Originally Posted by Taerom
42
+1
43!

I don't think I could simplify it further myself, but I'm not very good at math anyway. Why can't you use it as it is?
CdCf is offline   Reply With Quote
Old 05-21-07, 03:47 PM   #12
ManBearPig
1/2 man,1/2 bear,1/2 pig
Thread Starter
 
ManBearPig's Avatar
 
Join Date: May 2004
Location: .
Bikes: .
Posts: 1,122
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I guess I could - but if there were a generally known trigonometric identity in the field, it might look dumb for me to express it in an unnecessarily complicated fashion (e.g., to make something up, suppose everythinig in the parantheses could be replaced by cos(x/y) or something simple like that).
__________________
...
ManBearPig is offline   Reply With Quote
Old 05-21-07, 03:49 PM   #13
KingTermite 
On my TARDIScycle!
 
KingTermite's Avatar
 
Join Date: Jun 2005
Location: Eastside Seattlite Termite Mound
Bikes: Trek 520, Trek Navigator 300, Peugeot Versailles PE10DE
Posts: 3,924
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Towlie
I am 33 yrs old; I am not doing homework; I am a BSME (UT Austin, May, 1997)....I derived this expression trigonometrically on a project I am working on, and I don't know/remember how to simplify it.

I don't remember all the trigonometric identities because I haven't worked with them for a long while, e.g.

http://www.sosmath.com/trig/Trig5/trig5/trig5.html
I'm only calling it how it looked. See it from "our" point of view. Too many kids come on here and try to get help with their homework....quite often. It would be good for you to explain your situation so we don't think (like I did) that you are a 16 year old looking for homework help. I'm sorry if I offended....but that sure is how it looked.
__________________
Quote:
Originally Posted by coffeecake View Post
- it's pretty well established that Hitler was an *******.
KingTermite is offline   Reply With Quote
Old 05-21-07, 03:56 PM   #14
mtnbk3000
Senior Member
 
mtnbk3000's Avatar
 
Join Date: May 2007
Bikes:
Posts: 1,072
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by scrapmetal
what else ..... and thanks for the fish.
whats up with people and hitchikers guide to the galaxy
mtnbk3000 is offline   Reply With Quote
Old 05-21-07, 04:10 PM   #15
lyeinyoureye
Senior Citizen
 
lyeinyoureye's Avatar
 
Join Date: Feb 2005
Location: no
Bikes: yes
Posts: 1,347
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
If you actually have a BSME, then you should now how to do this as a matter of course imo. Nothing scares me more than engineering majors that don't know their shiz, because it's an applied skill. Unlike something like english, or even pure math, where screw ups can result in poor marks or scathing peer reviews, but shiz can't really go that bad from a practical perspective. Heh, ManBearPig.
lyeinyoureye is offline   Reply With Quote
Old 05-21-07, 04:43 PM   #16
EJ123
'05 NUEser
 
EJ123's Avatar
 
Join Date: Aug 2005
Bikes:
Posts: 3,370
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Answers.yahoo.com
EJ123 is offline   Reply With Quote
Old 05-21-07, 04:44 PM   #17
Tom Stormcrowe
Out fishing with Annie on his lap, a cigar in one hand and a ginger ale in the other, watching the sunset.
 
Tom Stormcrowe's Avatar
 
Join Date: Mar 2006
Location: South Florida
Bikes: Techna Wheelchair and a Sun EZ 3 Recumbent Trike
Posts: 16,120
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Towlie
If you can, please simplify this expression:

SQRT(X^2 + Y^2) * COS(45 - ATAN(Y/X))



The expression in the COS( ) looks familiar to me, but it has been 10 years since I finished my engineering degree. Thanks!
(XY)1/2*COS[45-ATANG(Y/X)]
=(XY)(XY)(COS)(45-X/Y)?

I think that's how it would factor out.
__________________
. He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you.- Fredrick Nietzsche

"We can judge the heart of a man by his treatment of animals." - Immanuel Kant
Tom Stormcrowe is offline   Reply With Quote
Old 05-22-07, 03:52 AM   #18
j-dowsett
Senior Member
 
Join Date: May 2005
Location: Salisbury, UK
Bikes: Decathlon R 7.4
Posts: 55
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
It'll give you the length of the vector from the origin to (x,y) projected onto the line x = y.

Though that might be how you derived it in the first place! Simplifying it?
Hmm, thinking dot product could be useful, (also thinking as typing so bear with me).

(x,y).(0.707, 0.707) = 0.707x + 0.707y

excel confirms.
where 0.707 is actually meant to be 1/sqrt(2)


Possible complications outside of the range 0-90 degrees due to the atan not being unique. Can't be bothered to think that hard though.


Apologies to those arguing the poster should have solved it themselves. But I needed some mental exercise due to having been laid up in hospital for four weeks avoiding my maths lectures.




edit:

Just managed it properly too.
let sqrt() denote SQRT(X^2 + Y^2) for easy writing.

SQRT(X^2 + Y^2) * COS(45 - ATAN(Y/X))

=sqrt() * [ cos(45)*cos(atan(y/x) + sin(45)*sin(atan(y/x)]
=sqrt() * [ 0.707 * x / sqrt() + 0.707 * y / sqrt() ]
=0.707 * (x + y)

Last edited by j-dowsett; 05-22-07 at 07:01 AM.
j-dowsett is offline   Reply With Quote
Old 05-24-07, 08:03 PM   #19
ManBearPig
1/2 man,1/2 bear,1/2 pig
Thread Starter
 
ManBearPig's Avatar
 
Join Date: May 2004
Location: .
Bikes: .
Posts: 1,122
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by j-dowsett
It'll give you the length of the vector from the origin to (x,y) projected onto the line x = y.

Though that might be how you derived it in the first place! Simplifying it?
Hmm, thinking dot product could be useful, (also thinking as typing so bear with me).

(x,y).(0.707, 0.707) = 0.707x + 0.707y

excel confirms.
where 0.707 is actually meant to be 1/sqrt(2)


Possible complications outside of the range 0-90 degrees due to the atan not being unique. Can't be bothered to think that hard though.


Apologies to those arguing the poster should have solved it themselves. But I needed some mental exercise due to having been laid up in hospital for four weeks avoiding my maths lectures.




edit:

Just managed it properly too.
let sqrt() denote SQRT(X^2 + Y^2) for easy writing.

SQRT(X^2 + Y^2) * COS(45 - ATAN(Y/X))

=sqrt() * [ cos(45)*cos(atan(y/x) + sin(45)*sin(atan(y/x)]
=sqrt() * [ 0.707 * x / sqrt() + 0.707 * y / sqrt() ]
=0.707 * (x + y)

Thanks, man. I actually logged in because I found the answer on my own and wanted to post it. The result I found was (X+Y) / SQRT(2). Soooooo simple. I found the answer numerically, plugging in numbers into a table and playing around with them.
__________________
...
ManBearPig is offline   Reply With Quote
Old 05-25-07, 05:06 AM   #20
Nicodemus
Feral Member
 
Nicodemus's Avatar
 
Join Date: Apr 2004
Location: Roma, Italia
Bikes: yes, I have one.
Posts: 2,666
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 11 Post(s)
ouch. math. I mean, I love it and all but I've done my time. University flashbacks
__________________
Quote:
Originally Posted by KrisPistofferson View Post
Did you just say "minarchist?" I'm going to start a 10-page vaginathon because only Libertarians can define Libertarianism. Also, you're mean.
Nicodemus is offline   Reply With Quote
Old 05-25-07, 09:04 AM   #21
joeprim
Senior Member
 
joeprim's Avatar
 
Join Date: Jan 2002
Location: Northern Neck Tidewater Va.
Bikes:
Posts: 1,688
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Towlie
If you can, please simplify this expression:

SQRT(X^2 + Y^2) * COS(45 - ATAN(Y/X))



The expression in the COS( ) looks familiar to me, but it has been 10 years since I finished my engineering degree. Thanks!
Where are you trying to get to? The Atan will give you and angle that you then subtract from 45 get the Cos of that ...
So as long as you know x&y things should be ok. Or are you trying to use this to determine x&y?

Joe
joeprim is offline   Reply With Quote
Old 05-25-07, 07:43 PM   #22
junkyard
Fourth Degree Legend
 
junkyard's Avatar
 
Join Date: Jun 2005
Location: American Gardens Building
Bikes: 2005 Kona Cinder Cone & 2010 Cannondale SuperSix
Posts: 3,826
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
42
4*2
8
junkyard is offline   Reply With Quote
Old 05-25-07, 08:07 PM   #23
Tom Stormcrowe
Out fishing with Annie on his lap, a cigar in one hand and a ginger ale in the other, watching the sunset.
 
Tom Stormcrowe's Avatar
 
Join Date: Mar 2006
Location: South Florida
Bikes: Techna Wheelchair and a Sun EZ 3 Recumbent Trike
Posts: 16,120
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by joeprim
Where are you trying to get to? The Atan will give you and angle that you then subtract from 45 get the Cos of that ...
So as long as you know x&y things should be ok. Or are you trying to use this to determine x&y?

Joe
I have no idea, I got lost at that point!
__________________
. He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you.- Fredrick Nietzsche

"We can judge the heart of a man by his treatment of animals." - Immanuel Kant
Tom Stormcrowe is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 10:35 AM.