Change Forum... Civil Aviation Travel, Polls & Prefs Tech/Ops Aviation Hobby Aviation Photography Photography Feedback Trip Reports Military Av & Space Non-Aviation Site Related LIVE Chat My Starred Topics | Profile | New Topic | Forum Index | Help | Search
 Hey Everybody, It's Time To Help Me With Calc!
 SSTjumbo From , joined Dec 1969, posts, RR: Posted Fri Nov 30 2001 04:32:53 UTC (14 years 6 months 4 days 2 hours ago) and read 2445 times:

 If y=f(x) and m=Dx/Dy, how do I find Dm/Dy? For instance, say y=x^2+3x+2 making Dy/Dx=2x+3 => m=2x+3, how would I find Dm/Dy? Does it involve natural logs maybe?
 PanAm747 From United States of America, joined Feb 2004, 4242 posts, RR: 8 Reply 1, posted Fri Nov 30 2001 05:50:28 UTC (14 years 6 months 4 days ago) and read 2416 times:

 Dy=2x+3 Dm=2 Dm/Dy=(2)/(2x+3) I believe you have two equations and you just divide them: 1. y=f(x)=x^2+3x+2= Dy=2x+3 2. m=f(x)=2x+3 Dm=2 Then: Dm/Dy=(2)/(2x+3)
 Pan Am:The World's Most Experienced Airline - P(oor) S(ailor's) A(irline): San Diego's Hometown Airline-Catch Our Smile!
 Boeing757fan From , joined Dec 1969, posts, RR: Reply 2, posted Fri Nov 30 2001 06:00:38 UTC (14 years 6 months 4 days ago) and read 2412 times:

 No, this is what it is... weopfjW+EPIJHSWIFJP -/EP'IFHwp[evgjwrpsvg pdihnifjvw[PG 23-4098T-3 'PGJP   Just holla holla if you need some more help.
 Docpepz From Singapore, joined May 2001, 1971 posts, RR: 3 Reply 3, posted Fri Nov 30 2001 06:07:22 UTC (14 years 6 months 4 days ago) and read 2407 times:

 You do have to realise that dy/dx is NOT a division, even though in many cases it may seemingly look like one. anyway you said that m = dx/dy. y=x^2+3x+2 making Dy/Dx=2x+3 => m=2x+3 why is m = 2x + 3? because if dy/dx = 2x +3, m is not 2x + 3, since you defined m as dx/dy. which makes m 1/(2x+3) unless it's a typo on your part. However, assuming it's not a typo: dm/dy = (dx/dy) x (dm/dx) dy/dx = 2x + 3 dx/dy = m = 1/(2x+3) dm/dx = 2/(2x+3)xY2 multiply dx/dy by dm/dx to get the answer. By this i am assuming that you correctly defined m as dx/dy and not dy/dx.
 SSTjumbo From , joined Dec 1969, posts, RR: Reply 4, posted Sat Dec 1 2001 05:31:00 UTC (14 years 6 months 3 days 1 hour ago) and read 2389 times:

 OOPS, I meant m=Dy/Dx!!! my bad
 Docpepz From Singapore, joined May 2001, 1971 posts, RR: 3 Reply 5, posted Sat Dec 1 2001 05:49:10 UTC (14 years 6 months 3 days ago) and read 2380 times:

 SSTjumbo: even if you meant dx/dy, the question can still be done, and is interesting. You should solve the question the same way. (dm/dy) = (dx/dy) x (dm/dx) You should still solve it that way. Except, since m is defined as dy/dx, you should define m, and use the formula (dx/dy) = (inverse of dy/dx) to solve it. Hope it helps. and regarding what PanAm747 said, I may be wrong, but dy= 2x+3 dx, and not 2x+3. It is wrong to write dy=2X+3 alone. thus dy/dx= 2X+3. It's quite important we learn not to forget the 'dx' term, especially in integration. Have you learnt integration by parts or by substitution? If you have, you'll know why.
 JetService From United States of America, joined Feb 2000, 4798 posts, RR: 10 Reply 6, posted Sat Dec 1 2001 14:17:40 UTC (14 years 6 months 2 days 16 hours ago) and read 2366 times:

 Simplify this way to find Dm/Dy.. (to find Dm/Dy, assuming y=f(x) and m=Dx/Dy... using variable 'S') Muliply both sides by 'd' S=d(y)/fm(x/y) Now variable use 'S' again to bring 1/m over SS=Dm(y)/f(x/y) Simplify 'y' (using variable 'k') SS=Dm/fk(x) Now using your 'for instance' result (=> m=2x+3), reduce 'x' by variable 'T' divided by (b/c) and you get the answer. SST = Dmb/Fck   Does it involve natural logs maybe? Save your natural logs for Sunday Morning.
 Delta-flyer From United States of America, joined Jul 2001, 2682 posts, RR: 6 Reply 7, posted Sat Dec 1 2001 20:50:40 UTC (14 years 6 months 2 days 9 hours ago) and read 2355 times:

 SSTjumbo, I think you have misstated the problem. I suspect the question is to solve for dm/dx, which is nothing but the second derivative of y with respect to x. If the problem is correctly stated, then you must first find x as a function of y. Since m = dy/dx, you can easily get that by differentiating f(x). Next, substitute for x so you get m as a function of y, not x. Then you can differentiate with respect to y to get dm/dy. But the problem is that getting x as a function of y gets tough if y=f(x) is greater than a first order equation, as in your example. Cheers, Pete
 "In God we trust, everyone else bring data"
 KROC From , joined Dec 1969, posts, RR: Reply 8, posted Sat Dec 1 2001 20:55:22 UTC (14 years 6 months 2 days 9 hours ago) and read 2354 times:

 What do you mean "Hey Everybody, It's Time To Help Me With Calc!" You make it sould like we have no chice. We help you or die. Well son, here is my offering... http://www.casio.com/calculators/product.cfm?section=24&market=0&product=1865
 Bernard Shakey From United States of America, joined Oct 2001, 561 posts, RR: 8 Reply 9, posted Sat Dec 1 2001 21:14:51 UTC (14 years 6 months 2 days 9 hours ago) and read 2351 times:

 With all due respect to SST, Jetservice that was classic.
 SSTjumbo From , joined Dec 1969, posts, RR: Reply 10, posted Sun Dec 2 2001 05:28:07 UTC (14 years 6 months 2 days 1 hour ago) and read 2334 times:

 That's right, you have to help me or else I'll kill you.
 SSTjumbo From , joined Dec 1969, posts, RR: Reply 11, posted Sun Dec 2 2001 05:32:10 UTC (14 years 6 months 2 days 1 hour ago) and read 2331 times:

 SST = Dmb/Fck Please mathematically prove this.
 JetService From United States of America, joined Feb 2000, 4798 posts, RR: 10 Reply 12, posted Sun Dec 2 2001 05:36:01 UTC (14 years 6 months 2 days 1 hour ago) and read 2328 times:

 LOL, SST!!!!! I can't! That batteries in my abacus just ran dry.
 Top Of Page Change Forum... Civil Aviation Travel, Polls & Prefs Tech/Ops Aviation Hobby Aviation Photography Photography Feedback Trip Reports Military Av & Space Non-Aviation Site Related LIVE Chat Forum Index

This topic is archived and can not be replied to any more.

Printer friendly format

 Similar topics: More similar topics...
Anyone Here Want To Help Me With My Math? posted Mon Sep 13 2004 17:05:40 by KLM672
Is It Time To Think Outside Of Aviation For Me? posted Mon Nov 24 2008 05:57:18 by KLM672
SaST: When Is It Time To Fill Your Gas Tank? posted Sat Aug 28 2010 18:57:37 by 2707200X
It's Begining To Annoy Me........ posted Thu Dec 3 2009 10:38:33 by KiwiRob
Is It OK To Pronounce Me-hi-co For Mexico? posted Thu May 7 2009 21:25:29 by Geekydude
Is It Time To Change Car Dealership Model? posted Wed Feb 18 2009 17:27:46 by NorthstarBoy
It's Time To Liberate Zimbabwe.. posted Mon Dec 22 2008 13:47:58 by Beaucaire
Help Me With A Tattoo... posted Sat Oct 25 2008 23:12:14 by PilotNTrng
Attn: Computer Geeks Please Help Me With My Build posted Wed Dec 26 2007 18:20:50 by Boeinglover24
Could Anyone Help Me With My New IMac? posted Fri Aug 17 2007 23:51:30 by Aero145