maths help...

angie88

General

08 Jan 06 15:30

angie88

omnipresent

Joined: 29 Oct 04
Moves: 20009

08 Jan 06 15:30

3 edits

Heya...
Somehow, I'm having a disagreement with the solutions I have fot a sample AP Calculus test I'm currently working on.
The question: Integral (x² cos(x³ )) dx= ?

I get the answer that it's (x³/3)*sin(x³ )+C
but the answer sheet is telling me that the answer is
(1/3)*sin(x³ )+C

Does anybody else get my answer, or can anybody explain why my answer is wrong (if it's wrong)?

Thanks 😀

Edits: getting rid of the winking smilies... weird that it should do that 😕

stocken

Joined: 23 Sep 05
Moves: 11774

08 Jan 06 15:37

Originally posted by angie88
Heya...
Somehow, I'm having a disagreement with the solutions I have fot a sample AP Calculus test I'm currently working on.
The question: Integral (x² cos(x³😉) dx= ?

I get the answer that it's (x³/3)*sin(x³😉+C
but the answer sheet is telling me that the answer is
(1/3)*sin(x³😉+C

Does anybody else get my answer, or can anybody explain why my answer is wrong (if it's wrong)?

Thanks 😀

Would you please stop winking at me? 😉

Siskin

over your head

Joined: 12 Jul 04
Moves: 23004

08 Jan 06 15:39

1 edit

The easiest way to check the solution to an integral is to differentiate it and see if you come up with original function.

Wibble Wobble

Action barbie

Ka-koogy

Joined: 03 Jan 06
Moves: 6678

08 Jan 06 15:39

Originally posted by stocken
Would you please stop winking at me? 😉

😵😵😵😵😵😵😵😵😵😵😵😵😵😵😵😵😵😵😵😵😵😵😵😵😵😵😵

Coconut

Earth Prime

Joined: 16 Mar 05
Moves: 35265

08 Jan 06 15:42

1 edit

Your answer is wrong. Work backwards to check it. To take the derivitive of (1/3)*sin(x^3)+C, remember that you must take the derivitive of x^3 and put it out front of the sin function (cos after you have differentiated). So that is of course 3x^2. Multiplied by the (1/3) before the sin gives us the original derivitive.

rhb

Ginger Scum

Paranoia

Joined: 23 Sep 03
Moves: 15902

08 Jan 06 16:02

Have you not realised yet that all of this has very little practical application in the real world?

So long as you can stay ontop of household chores, get up in time to get to work each day, and balance your bank statement at the end of each month the rest kinda takes care of itself.

🙂

Coconut

Earth Prime

Joined: 16 Mar 05
Moves: 35265

08 Jan 06 16:09

Originally posted by rhb
balance your bank statement at the end of each month

uh oh. Do most people actually do that still? My bank statements are in the trash.

angie88

omnipresent

Joined: 29 Oct 04
Moves: 20009

08 Jan 06 16:12

Originally posted by rhb
Have you not realised yet that all of this has very little practical application in the real world?

So long as you can stay ontop of household chores, get up in time to get to work each day, and balance your bank statement at the end of each month the rest kinda takes care of itself.

🙂

Yes I know, I don't really care about it. But I'm doing it because I hope haveing completed an AP Calculus course (along with an AP English course) will help get me into a good uni so that I can attemp the things you mentioned in the first place.

Oh, and thanks Coconut 😀

Dr Strangelove

Joined: 22 Aug 05
Moves: 26450

08 Jan 06 16:39

1 edit

Originally posted by rhb
Have you not realised yet that all of this has very little practical application in the real world?

Almost all modern business, science, and medicine relies on calculus.

rhb

Ginger Scum

Paranoia

Joined: 23 Sep 03
Moves: 15902

09 Jan 06 23:31

Originally posted by angie88
Yes I know, I don't really care about it. But I'm doing it because I hope haveing completed an AP Calculus course (along with an AP English course) will help get me into a good uni so that I can attemp the things you mentioned in the first place.

Oh, and thanks Coconut 😀

If you get to clean bogs you can do everything I mentioned. Aim high though 🙂

rhb

Ginger Scum

Paranoia

Joined: 23 Sep 03
Moves: 15902

09 Jan 06 23:32

Originally posted by Dr Strangelove
Originally posted by rhb
[b]Have you not realised yet that all of this has very little practical application in the real world?

Almost all modern business, science, and medicine relies on calculus.[/b]

Maybe, I work in modern business and never needed it though. None of my colleagues did either (i asked).

nickhawker

Joined: 08 Feb 05
Moves: 13312

10 Jan 06 00:44

1 edit

Originally posted by rhb
Have you not realised yet that all of this has very little practical application in the real world?

So long as you can stay ontop of household chores, get up in time to get to work each day, and balance your bank statement at the end of each month the rest kinda takes care of itself.

🙂

Maybe if you only intend to learn arithmatic, maths is far FAR different.

Moldy Crow

Your Eminence

Scunthorpe

Joined: 16 Dec 04
Moves: 13395

10 Jan 06 00:50

Originally posted by angie88
Heya...
Somehow, I'm having a disagreement with the solutions I have fot a sample AP Calculus test I'm currently working on.
The question: Integral (x² cos(x³ )) dx= ?

I get the answer that it's (x³/3)*sin(x³ )+C
but the answer sheet is telling me that the answer is
(1/3)*sin(x³ )+C

Does anybody else get my answer, or can anybody explain why my ans ...[text shortened]...

Thanks 😀

Edits: getting rid of the winking smilies... weird that it should do that 😕

When did they start using letters in math ?

rhb

Ginger Scum

Paranoia

Joined: 23 Sep 03
Moves: 15902

10 Jan 06 00:55

Originally posted by nickhawker
Maybe if you only intend to learn arithmatic, maths is far FAR different.

Is 'FAR' an operator, like 'AND' or 'OR'?

I'd be confused but I'm more concerned about (re)solving Fermats' last theorem.

Dr Strangelove

Joined: 22 Aug 05
Moves: 26450

10 Jan 06 01:03

Originally posted by rhb
Maybe, I work in modern business and never needed it though. None of my colleagues did either (i asked).

You might not need to use it personally in your business but almost certainly if someone hadn't studied it and used it in one way or another, your business would not run as efficiently as it does now.