[windows2000] Re: OT - Math Question

  • From: Moby <moby@xxxxxxxxxxxxxx>
  • To: windows2000@xxxxxxxxxxxxx
  • Date: Wed, 29 Nov 2006 15:18:33 -0600



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

--
--Moby

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