# How do you differentiate f(x)=(1+tan^2x)/secx?

Oct 31, 2016

$f \left(x\right) = \frac{1 + {\tan}^{2} x}{\sec} x$

$= {\sec}^{2} \frac{x}{\sec} x$

$= \sec x$

Which means that:

$f ' \left(x\right) = \sec x \tan x$

Watch this video to find out how to differentiate secx:

You may also need to see some handy trigonometric rules .