Math Help

[whytheheckme]

I searched, to no avail, however my time is limited.

I have the equation:

x = (1+e^y) / (1-e^y)

and I need to solve for y. Using the TI, I get the solution as:

y = ln( (x-1) / (x+1) )

But I need to know how to do it by hand. I took Calculus 1 so long ago, I just simply forgot the steps. Any assistance would be much appreciated.

Thanks!
Jacob

[m^3]

Correct me if I'm wrong, but this seems right:

x = (1 + e^y) / (1 - e^y)
x(1 - e^y) = (1 + e^y)
x - x(e^y) = 1 + e^y
x - 1 = e^y + x(e^y)
x - 1 = (x + 1)(e^y)
(x - 1) / (x + 1) = e^y
y = ln( (x - 1) / (x + 1) )

first post =P

[whytheheckme]

How is this step performed?

x - x(e^y) = 1 + e^y
x - 1 = (x + 1)(e^y)

Nvm, I just realized.

THANK YOU VERY MUCH!

Very nice first post! Welcome to the CD community!

~Jacob

[Joe Ross]

How is this step performed?

x - x(e^y) = 1 + e^y
x - 1 = (x + 1)(e^y)

I performed it as two steps


x - x(e^y) = 1 + e^y
x - 1 = xe^y + e^y
factor the e^y out
x -1 = (x + 1)(e^y)

[whytheheckme]

m^3, Joe and Greg, you guys ROCK!

I'm tutoring Calculus, and I was helping a student when we ran into this section of a problem.

By the way, is there a math help thread that I'm, missing (cuz I did search), or is math help something new here?

Jacob

[Greg Needel]

I hope that all of our new members are as helpful as the one above. We will be in for an amazing season if that is the case.

[m^3]

Thanks!

I hope it will be an amazing season too; with the new control system, I'm anxious to see what they do with the game (autonomous, etc...).

I actually meant to put those steps in... Edited my post right as you asked =P

Is there a math thread? I don't know...
If I have trouble, typing equations into Google sometimes yields similar equations that can help you solve the original.

Michael

[R.C.]

I hope that all of our new members are as helpful as the one above. We will be in for an amazing season if that is the case.

I second that.

[JaneYoung]

I'm tutoring Calculus, and I was helping a student when we ran into this section of a problem.


It is a wise tutor/mentor who knows when to ask for help. Knowledge can continue to be gained/shared that way.

[JesseK]

...and I need to solve for y. Using the TI, I get the solution as:

y = ln( (x-1) / (x+1) )

But I need to know how to do it by hand. I took Calculus 1 so long ago, I just simply forgot the steps. Any assistance would be much appreciated.

Thanks!
Jacob

<3 TI-89

My brother got me a book of mathematical lookup tables for Christmas one year, since I was destined to go so far in math. First year of college, my girlfriend at the time swapped her TI-89 for my TI-83 since she her course was teaching exact steps for a TI-83, and I wanted a TI-89 for Calc. I havne't used that book ever since. Unfortunately, I've also forgotten some of the more rudimentary algebraic tricks -- like I know there's an expression you can multiply the top and bottom of the original equation by in order to *easily* extract the y from it -- but I can't remember the trick to figure it out :o

[ManicMechanic]

By the way, is there a math help thread that I'm, missing (cuz I did search), or is math help something new here?

Jacob

How about the Math & Science thread (http://www.chiefdelphi.com/forums/forumdisplay.php?f=70)?