Math Is Fun Forum

ineedhelpwithcalc

Guest

Need Help With Calc.

OK, I have loads of questions to do with Calc.

1) I don't completely understand definite integration. Do we only need to use the rectangle/trapezium rules if it specifies a number of portions to cut the area under the function into?
2)

ineedhelpwithcalc

Guest

Re: Need Help With Calc.

Sorry 'bout that. I pressed submit instead of preview!

I'm terrible with latex, so I've partially done it:

2)

(x[sup]2[/sup]+1)dx

I think I know how to do this, but I might be wrong.

I split it up into two integrals..... right?

ineedhelpwithcalc

Guest

Re: Need Help With Calc.

Why isn't it working when I type in the math?

ineedhelpwithcalc

Guest

Re: Need Help With Calc.

2)

(x[sup]2[/sup]+1)dx

I split this into two parts.

(x[sup]2[/sup]) +

(1)

And then I integrate both? What answer should I get?

ineedhelpwithcalc

Guest

Re: Need Help With Calc.

I got 38/3 as my answer, is that right? If not, please show me the correct process. I'm pretty sure I did F(b)-F(a) for each part correctly.

Also, could someone please tell me about surface integrals for a newbie. Anything to get me started. Thanks!

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Need Help With Calc.

Hi ineedhelpwithcalc:

I cannot see the problem: but if this is want:

The answer is 32 / 3 not 38 / 3.

Last edited by bobbym (2009-11-21 09:30:26)

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

gckc123

Member

Registered: 2009-10-19

Posts: 15

Re: Need Help With Calc.

the answer is 32/3
What is your F(x)?

It should be x^3 + x

Cheers

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Maths is fun!

simplyjasper

Member

Registered: 2009-11-15

Posts: 24

Re: Need Help With Calc.

2)

(x[sup]2[/sup]) +

(1)

And then I integrate both? What answer should I get?

If you do it your way, it should go

You can check where u made a mistake in your integration and don't do it during your exam

simplyjasper

Member

Registered: 2009-11-15

Posts: 24

Re: Need Help With Calc.

OK, I have loads of questions to do with Calc.

1) I don't completely understand definite integration. Do we only need to use the rectangle/trapezium rules if it specifies a number of portions to cut the area under the function into?
[/math]

Rectangle/Trapezium Rule and there's an additional Simpson's Rule... (Or that's what I have came across through my limited years of studies in Math)
They are usually used for the estimation of an integration and don't usually provide the exact value

How these all came out is due to the Riemann sum, you may wish to read up a little bit on them ...

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Need Help With Calc.

Hi ineedhelpwithcalc;

1) I don't completely understand definite integration. Do we only need to use the rectangle/trapezium rules if it specifies a number of portions to cut the area under the function into?

You can think of definite integration as the area under a curve. You only need to use the trapezoid or rectangular rule when you cannot integrate the function analytically. Your integral above can be done analytically to obtain an exact answer.

The rectangular rule, trapezoidal rule, simpsons rule ( 3/8 or otherwise), newton's coates formulas, romberg integration. gaussian integration and all the others are methods to numerically find the area under a curve.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

ineedhelpwithcalc

Guest

Re: Need Help With Calc.

Thanks!

I've been studying definite integration for about 10 hours today...ie, different rules, such as inverse tangent rule, and integration by parts. But I still have some questions...

1) What is vector calculus, and how can I get started on it?
2) What does surface integration do, and what is the notation?
3) Is a double or triple integral just calculating two or three separate areas under a curve or something else?
4) This is about 3D co-ordinates visually. How are you supposed to read them if the unit squares aren't supplied? I find it so hard to find out where the depth *is* actually pointing to.

Thanks guys.

ineedhelpwithcalc

Guest

Re: Need Help With Calc.

Also, sorry to be a bother, but what the heck does this symbol mean? A different from of integration?