# Math Help - finding y'

1. ## finding y'

$

y = \frac{e^x - e^{-x}}{e^x + e^{-x}}
$

use the quotient rule and get:

$

y' = \frac{(e^x + e^{-x}) \cdot (e^x - e^{-x}) \cdot (-1) - (e^x - e^{-x}) \cdot (e^x + e^{-x}) \cdot (-1)}{(e^x + e^{-x})^2}
$

but when i simplify this, i get 0
what am i doing wrong...

2. what am i doing wrong...
you're not taking the derivative correctly ...

the derivative of $e^x - e^{-x}$ is $e^x - e^{-x}\cdot -1 = e^x + e^{-x}$

the derivative of $e^x + e^{-x}$ is $e^x + e^{-x}\cdot -1 = e^x - e^{-x}$

$
y = \frac{e^x - e^{-x}}{e^x + e^{-x}}
$

use the quotient rule

$
y' = \frac{(e^x + e^{-x}) \cdot (e^x + e^{-x}) - (e^x - e^{-x}) \cdot (e^x - e^{-x})}{(e^x + e^{-x})^2}
$