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Education > Math Undergrad > guidance..Show ...
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guidance..Show using Riemann sums d/dr[A]=2pi*r (A=area circle)

by gottaquestion <Jmcdon11@[EMAIL PROTECTED] > Mar 3, 2008 at 11:15 PM

This was posed as an extra credit problem.  I tried a hodge podge
explanation with a picture, some shading, and some integral signs, but it
didn't fly.  Think Riemann sums he said.  So I have.  but I'm not sure
what to do.  I used definition of the indefinite integral using Riemann
sums.  I cannot really see what happens to the n.  This is tough
expressing without proper symbols but Ill do my best.  
heres what I did:
limit Summation i=1 n=infinity f(x)*(b-a)/n
f(x)= +/-sq rt(r^2-x^2) and (b-a)/n = 2r/n
then I said x=r*sin(@[EMAIL PROTECTED]
) so then f(x)= r*cos(@[EMAIL PROTECTED]
)...I used a triangle and went
back into x, but am I at least on the right track?  Isnt the goal hear to
get 1/n to go to zero?  But not the whole thing, because I know that I
want to arrive at 2pi*r  is the trick to multiply by the conjugate or
something?
 




 10 Posts in Topic:
guidance..Show using Riemann sums d/dr[A]=2pi*r (A=area circle)
gottaquestion <Jmcdon1  2008-03-03 23:15:49 
Re: guidance..Show using Riemann sums d/dr[A]=2pi*r (A=area circ
Paul Sperry <plsperry@  2008-03-04 04:33:56 
Re: guidance..Show using Riemann sums d/dr[A]=2pi*r (A=area circ
gottaquestion <Jmcdon1  2008-03-03 23:51:04 
Re: guidance..Show using Riemann sums d/dr[A]=2pi*r (A=area circ
gottaquestion <Jmcdon1  2008-03-03 23:53:20 
Re: guidance..Show using Riemann sums d/dr[A]=2pi*r (A=area circ
gottaquestion <Jmcdon1  2008-03-04 00:24:59 
Re: guidance..Show using Riemann sums d/dr[A]=2pi*r (A=area circ
Frederick Williams <&q  2008-03-05 14:10:49 
Re: guidance..Show using Riemann sums d/dr[A]=2pi*r (A=area circ
gottaquestion <Jmcdon1  2008-03-03 23:31:33 
Re: guidance..Show using Riemann sums d/dr[A]=2pi*r (A=area circ
gottaquestion <Jmcdon1  2008-03-03 23:39:02 
Re: guidance..Show using Riemann sums d/dr[A]=2pi*r (A=area circ
gottaquestion <Jmcdon1  2008-03-03 23:39:41 
Re: guidance..Show using Riemann sums d/dr[A]=2pi*r (A=area circ
"Ronald Lett" &  2008-03-04 16:17:56 

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tan12V112 Wed Dec 3 18:50:32 CST 2008.