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NotAProdigy

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Sep 10, 2009
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buklau said:
What's so special about this integral? It seems relatively simple...You're just multiplying two functions together, unless I'm missing something...

Derivatives are just slopes of functions, and integrals are just areas underneath (or between) functions.
Well YEAH. You could simply express it as this:


It's a valid answer, but I'm not looking for the area. I'm looking for the functions that can derive into f(x)*g(x). It's a bit too ineffable for me.
 

buklau

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Sep 10, 2009
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riskroWe said:
Have you not been taught how to integrate a product of two functions?
Be warned, it's fairly time consuming.
that really depends on the function... if the product is a polynomial (ie. x^3+2x+3) you could do it in seconds @_@
 

klakkat

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May 24, 2008
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Since this is an entirely general equation, I would solve this by Integration by Parts. Wiki it if you don't remember the technique (I assume you've been exposed to it if you're being asked to solve this problem).

It's a somewhat long exercise so I don't feel like copying it out here. Integration by parts does assume that f(x) and g(x) are continuous on the interval and differentiable on the interval, so you will need a different technique if that is not the case.
 

buklau

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Sep 10, 2009
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NotAProdigy said:
buklau said:
What's so special about this integral? It seems relatively simple...You're just multiplying two functions together, unless I'm missing something...

Derivatives are just slopes of functions, and integrals are just areas underneath (or between) functions.
Well YEAH. You could simply express it as this:


It's a valid answer, but I'm not looking for the area. I'm looking for the functions that can derive into f(x)*g(x). It's a bit too ineffable for me.
What you posted is just the limit definition of an integral, it would amount to the same thing I thought; multiply the functions together, take the integral, evaluate at the initial and final points...unless I am completely forgetting everything calculus related already lol. (reading other posts above mine, it appears I am :D)
 

AvsJoe

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May 28, 2009
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It's been a long time since I took that class. I don't even recognize half the symbols anymore.
Berethond said:
AHAHAHAHAHHA
Look at the post above yours.
MUAHAHAHAHA.
Ninja-ing at it's finest. Good work.
 

Sewblon

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Nov 5, 2008
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I wish I had finished Exploring Creation With Physics(it is the title of a textbook).
 

muckinscavitch

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Jul 27, 2009
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"Biology is just chemistry, chemistry is just physics, physics is just math, and math is just really hard." Quote: My first year chem prof

anyway, you have to do integration by parts

u = f(x) dv = g(x)dx
du = f(x)'dx v = integral of g(x)dx

then you do u*v - integral of (v*du)
so f(x)*g(x) - integral of [g(x)*{f(x)'}]

input and solve

you must still solve with A and B, so

f(x)*g(x)(solved from A to B) - integral (from a to be) of [g(x)*{f(x)'}]


you maybe have to repeat or continue with another technique.
 

teutonicman

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Mar 30, 2009
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your just integrating the product rule, for that problem you use the method of integration by parts. http://www.ugrad.math.ubc.ca/coursedoc/math101/notes/techniques/parts.html
 

Emeli

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Mar 9, 2009
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Wow... I didn't realise that the second I left highschool I completely blanked advanced maths from my memory. I know I've done similar equations before, but now I don't even know what I'm looking at.
 

stone0042

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Apr 10, 2009
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Wow, here i was thinking i was smart in math. Then again i am just a junior in high school and only in precalc.