[windows2000] Re: OT - Math Question
- From: Chris Berry <chris_berry-list-windows2000@xxxxxxxxxxxxxxxxx>
- To: windows2000@xxxxxxxxxxxxx
- Date: Wed, 29 Nov 2006 13:25:24 -0800
Moby wrote:
Chris Berry wrote:
Mark Lane wrote:
I was a math major in a former life 10+ years.
1/2(e^x + e^-x) = 4
e^x + e^-x = 8
(e^x)^2 + 1 = 8e^x
Let y = e^x such that x = ln(y).
y^2 + 1 = 8y
y^2 - 8y + 1 = 0
Use quadratic formula, which is x = (-b +- sqrt(b^2 - 4ac))/2a, to
solve for
y in previous equation. Then x = ln(y)
Pretty, but pure handwaving, you still didn't provide a value for x.
To continue the handwaving some more then :)
Using the quadratic formula and keeping only the positive value for y (y
= e^x - as such y cannot be negative!) we get:
y = (8 + 9.592) /2 = 8.796
This means e^x = 8.796 => x = ln(8.796) = 2.174
That doesn't work out right when I plug it into my spreadsheet.
*scratches head*
I used:
=1/2*(2.71828183^A1+2.71828183^(A1*-1))
and got
4.4536 not 4
I'm a little rusty though, did I miss something?
--
Chris Berry
chris_berry@xxxxxxxxxxxxxxxxx
Information Advisory Manager
JM Associates
"If we don't believe in freedom of expression for people we despise, we
don't believe in it at all." --Noam Chomsky
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