# How do i find the derivative of (cos^2(x))/(1-sin^2(x))?

Jan 26, 2015

The derivative of $f \frac{x}{g} \left(x\right)$ would be (Quotient Rule):

$\frac{f ' \left(x\right) g \left(x\right) - f \left(x\right) g ' \left(x\right)}{g \left(x\right)} ^ 2$

$1 - {\sin}^{2} \left(x\right) = {\cos}^{2} \left(x\right)$!!!!
So your function becomes: $\frac{{\cos}^{2} \left(x\right)}{{\cos}^{2} \left(x\right)} = 1$ with derivative equal to $0$!!!