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InvisibleThirdEyeOpening
Lost In My Head
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Folding@home Statistics
Registered: 08/24/04
Posts: 2,287
Loc: How the fuck should i kno... Flag
A problem i got wrong...
    #11188357 - 10/05/09 06:55 PM (8 years, 1 month ago)

....and not too sure why. I havent had a chance to talk to my prof, and no class tomorrow so im asking here.

ex + e-x = 7

I used u substitution after multiplying everything by ex

ex2 + 1 = 7ex
(should be e raised to x2)

u2 + 1 = 7u

then used quadratic equation and got

(7 +/- 3*5.5) / 2  (no idea how to put a radical sign in here so i just used x.5, but i wrote 3 radical 5)


--------------------

Only two things are infinite, the universe and human stupidity. Im not too sure about the former.      -Einstein

Of course the rules need to be enforced, but the goal of law and order should be to create a just society, not to enforce laws. -Unknown

“I contend that we are both atheists. I just believe in one fewer god than you do. When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours.”  -Stephen Roberts


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InvisibleDieCommie

Registered: 12/11/03
Posts: 29,043
Re: A problem i got wrong... [Re: ThirdEyeOpening]
    #11188799 - 10/05/09 07:45 PM (8 years, 1 month ago)

Dont forget to substitute that back into Formula: 0 and then solve for x.


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Offlineisaacein
exp(ix) = cosx + isinx


Registered: 05/21/08
Posts: 1,141
Last seen: 6 years, 8 months
Re: A problem i got wrong... [Re: ThirdEyeOpening]
    #11188914 - 10/05/09 08:06 PM (8 years, 1 month ago)

Your mistake is

Formula: 0

which should be

Formula: 1.

Note that Formula: 2 is Formula: 3.

Edit : it seems that although you made that mistake, you ended up with the correct equation in Formula: 4. So as DieCommie said, just substitute back.


--------------------
Formula: 0


Edited by isaacein (10/05/09 08:08 PM)


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InvisibleDieCommie

Registered: 12/11/03
Posts: 29,043
Re: A problem i got wrong... [Re: isaacein]
    #11188917 - 10/05/09 08:07 PM (8 years, 1 month ago)

I think he meant Formula: 0


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Offlineisaacein
exp(ix) = cosx + isinx


Registered: 05/21/08
Posts: 1,141
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Re: A problem i got wrong... [Re: DieCommie]
    #11188937 - 10/05/09 08:10 PM (8 years, 1 month ago)

Quote:

DieCommie said:
I think he meant Formula: 0




But he said
Quote:

(should be e raised to Formula: 1)




which is very different from Formula: 2.


--------------------
Formula: 0


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InvisibleDieCommie

Registered: 12/11/03
Posts: 29,043
Re: A problem i got wrong... [Re: isaacein]
    #11189104 - 10/05/09 08:31 PM (8 years, 1 month ago)

Yea, just trying to read between the lines.


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Offlineisaacein
exp(ix) = cosx + isinx


Registered: 05/21/08
Posts: 1,141
Last seen: 6 years, 8 months
Re: A problem i got wrong... [Re: DieCommie]
    #11189187 - 10/05/09 08:45 PM (8 years, 1 month ago)

Quote:

DieCommie said:
Yea, just trying to read between the lines.





...which apparently his professor didn't try :smirk:

I see your point though.


--------------------
Formula: 0


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InvisibleDieCommie

Registered: 12/11/03
Posts: 29,043
Re: A problem i got wrong... [Re: isaacein]
    #11189199 - 10/05/09 08:47 PM (8 years, 1 month ago)

I still think his problem was not back substituting.  I see students make that mistake alot.


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InvisibleThirdEyeOpening
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Posts: 2,287
Loc: How the fuck should i kno... Flag
Re: A problem i got wrong... [Re: isaacein]
    #11189219 - 10/05/09 08:50 PM (8 years, 1 month ago)

Quote:

isaacein said:
Quote:

DieCommie said:
I think he meant Formula: 0




But he said
Quote:

(should be e raised to Formula: 1)




which is very different from Formula: 2.





Yea i see how i goofed on the Formula: 2 tho i know my Formula: 4 sub was right.

I wrote my answer as Formula: 5

and was wrong, every other Formula: 6 was right, so i was confused how i got this one wrong. ( the Formula: 7 is just a random number tht the prof gave, on his other version of the test it was 6 instead of 7)


--------------------

Only two things are infinite, the universe and human stupidity. Im not too sure about the former.      -Einstein

Of course the rules need to be enforced, but the goal of law and order should be to create a just society, not to enforce laws. -Unknown

“I contend that we are both atheists. I just believe in one fewer god than you do. When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours.”  -Stephen Roberts


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InvisibleDieCommie

Registered: 12/11/03
Posts: 29,043
Re: A problem i got wrong... [Re: ThirdEyeOpening]
    #11189259 - 10/05/09 08:56 PM (8 years, 1 month ago)

hmmm well I dont know then.  Professors mess up sometimes too.  Maybe it was in your work with the error issacein pointed out, even though the answer came out.


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InvisibleThirdEyeOpening
Lost In My Head
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Folding@home Statistics
Registered: 08/24/04
Posts: 2,287
Loc: How the fuck should i kno... Flag
Re: A problem i got wrong... [Re: DieCommie]
    #11189308 - 10/05/09 09:01 PM (8 years, 1 month ago)

Yea i think im gonna bring it to him on Wed. i swear i did all my math right, which is why im confused.

i did resubstitute, and got the Formula: 0 of Formula: 1


I got an 88% on the test which is a good bit below my average, i really dont want a test on fucking logs to be my lowest test grade, that's just sad in my eyes, lol.


--------------------

Only two things are infinite, the universe and human stupidity. Im not too sure about the former.      -Einstein

Of course the rules need to be enforced, but the goal of law and order should be to create a just society, not to enforce laws. -Unknown

“I contend that we are both atheists. I just believe in one fewer god than you do. When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours.”  -Stephen Roberts


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InvisibleThirdEyeOpening
Lost In My Head
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Folding@home Statistics
Registered: 08/24/04
Posts: 2,287
Loc: How the fuck should i kno... Flag
Re: A problem i got wrong... [Re: ThirdEyeOpening]
    #11189363 - 10/05/09 09:09 PM (8 years, 1 month ago)

I do have another question tho.


Simplify

Formula: 0


I got to Formula: 1

ln x * ln y = ?  i dont recall any rules that simplify this


--------------------

Only two things are infinite, the universe and human stupidity. Im not too sure about the former.      -Einstein

Of course the rules need to be enforced, but the goal of law and order should be to create a just society, not to enforce laws. -Unknown

“I contend that we are both atheists. I just believe in one fewer god than you do. When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours.”  -Stephen Roberts


Edited by ThirdEyeOpening (10/05/09 09:10 PM)


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InvisibleThirdEyeOpening
Lost In My Head
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Folding@home Statistics
Registered: 08/24/04
Posts: 2,287
Loc: How the fuck should i kno... Flag
Re: A problem i got wrong... [Re: ThirdEyeOpening]
    #11189421 - 10/05/09 09:17 PM (8 years, 1 month ago)

lol, ok one more :grin:


Formula: 0
(Should be 3 raised to the Formula: 1)

i got to

Formula: 2


i think i over did this one and lost myself in simplifying.




I have an odd feeling im going to :facepalm: when i see the solutions.......


--------------------

Only two things are infinite, the universe and human stupidity. Im not too sure about the former.      -Einstein

Of course the rules need to be enforced, but the goal of law and order should be to create a just society, not to enforce laws. -Unknown

“I contend that we are both atheists. I just believe in one fewer god than you do. When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours.”  -Stephen Roberts


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Invisiblemozhual
Amateur Omnologist
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Registered: 09/26/09
Posts: 283
Loc: New England
Re: A problem i got wrong... [Re: isaacein]
    #11189817 - 10/05/09 10:20 PM (8 years, 1 month ago)

You guys better still be around when I go to college! Hehehe...


--------------------
"Nature is like a sculptor constantly improving upon her work, but to do so she chisels away at living flesh." H.K. Bloom

"Is God willing to prevent evil but not able? Then he is not omnipotent...
Is he able but not willing? Then he is malevolent...
Is he both able, and willing? Then whence cometh evil?
Is he neither able nor willing? Then why call him god." Epicurus c. 300 BCE

"When I brought up the fact that 'No drug is good or bad, they're all just A drug, what someone does with them determines the postive or negative outcome. Look at medicine, those are drugs' Reponse was that 'well medicine solves problems' well so does LSD." -Learningtofly


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InvisibleDieCommie

Registered: 12/11/03
Posts: 29,043
Re: A problem i got wrong... [Re: ThirdEyeOpening]
    #11190658 - 10/06/09 12:12 AM (8 years, 1 month ago)

Quote:

ThirdEyeOpening said:
I do have another question tho.


Simplify

Formula: 0


I got to Formula: 1

ln x * ln y = ?  i dont recall any rules that simplify this




Maybe this?
Formula: 2

In which case, (careful with the parenthesis)
Formula: 3


That is, if it is adding - if multiplying there is not much you can do.



Im not sure what the question is for your second one.  Express as logs?


Edited by DieCommie (10/06/09 02:45 AM)


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OfflineWasteland
Elektromeister!
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Registered: 07/26/06
Posts: 4,768
Loc: A pathetic small town in ...
Last seen: 4 years, 6 months
Re: A problem i got wrong... [Re: DieCommie]
    #11194611 - 10/06/09 05:36 PM (8 years, 1 month ago)

Maybe this would be a good place to ask this: As a HS graduate who got his diploma with a nearly sub-algebraeic knowledge of mathmatics, where might I begin in digital self education? (sites, subjects, concepts, algorithms, whatever you can tell me would help, I haven't a clue as to how I can get myself started on this.)


--------------------
CLICKY!!!
!
The Mad Shroomer said:
People are always promising the apocalypse. They never deliver. :frown:
http://superftmn.deviantart.com/gallery/


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Invisiblemozhual
Amateur Omnologist
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Registered: 09/26/09
Posts: 283
Loc: New England
Re: A problem i got wrong... [Re: Wasteland]
    #11194648 - 10/06/09 05:39 PM (8 years, 1 month ago)

<5 seconds on google brings up:
http://mathworld.wolfram.com/
and
http://www.math.com/
Both of which seem like rather extensive and well kept sites.

also if you are looking to learn the who and the why behind the what and the how, http://en.wikipedia.org/wiki/Mathematics has a lot to offer.


--------------------
"Nature is like a sculptor constantly improving upon her work, but to do so she chisels away at living flesh." H.K. Bloom

"Is God willing to prevent evil but not able? Then he is not omnipotent...
Is he able but not willing? Then he is malevolent...
Is he both able, and willing? Then whence cometh evil?
Is he neither able nor willing? Then why call him god." Epicurus c. 300 BCE

"When I brought up the fact that 'No drug is good or bad, they're all just A drug, what someone does with them determines the postive or negative outcome. Look at medicine, those are drugs' Reponse was that 'well medicine solves problems' well so does LSD." -Learningtofly


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Offlineisaacein
exp(ix) = cosx + isinx


Registered: 05/21/08
Posts: 1,141
Last seen: 6 years, 8 months
Re: A problem i got wrong... [Re: Wasteland]
    #11194685 - 10/06/09 05:44 PM (8 years, 1 month ago)

I strongly disadvise you from trying to learn on the internet. Mathworld and Wikipedia will only help you realize the extent of your ignorance.

If you tell me what you want to learn, I can suggest some real books. If you don't know where to start, tell me where you want to go and I'll try to point you in a suitable direction.

A good website however is Math Help Forum.


--------------------
Formula: 0


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OfflineWasteland
Elektromeister!
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Registered: 07/26/06
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Re: A problem i got wrong... [Re: isaacein]
    #11194835 - 10/06/09 06:05 PM (8 years, 1 month ago)

I am not certain which field of mathmatics I wish to delve into, the last I recall attempting (and failing miserably) to understand where "binomials.

I belieive that material existance is composed of chaotic patterns and fractal-like structures, I would like to understand more of their numerical side, and what all this intensely specific static about chaos is, that I run into without really understanding.

Also I wonder of digital encryption and binary encoding, electron flow schematics, and equations.


--------------------
CLICKY!!!
!
The Mad Shroomer said:
People are always promising the apocalypse. They never deliver. :frown:
http://superftmn.deviantart.com/gallery/


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Offlineisaacein
exp(ix) = cosx + isinx


Registered: 05/21/08
Posts: 1,141
Last seen: 6 years, 8 months
Re: A problem i got wrong... [Re: Wasteland]
    #11195379 - 10/06/09 07:25 PM (8 years, 1 month ago)

Well you should begin by the beginning! The two probably most single important things to learn are Calculus and Linear Algebra.

Probably the single best book to learn Calculus from is Micheal Spivak's Calculus. It has been around for a long time and it is a beautiful book, perfect for self-teaching. You should make sure you master your high-school math before attempting to jump in.

As for Linear Algebra, there are many possibilities; I learned it from Friedberg, Insel & Spence's Linear Algebra and I very much enjoyed the presentation. It is a fairly abstract book but if you can work your way through it you will gain a lot.


--------------------
Formula: 0


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