Hi

my book says the integral of tan x = ln |sec x|

When i do it:

tan x = sin x/cos x

integral sinx/cos x dx

let u = cos x

du = -sin x dx

- du = sin x dx

integral: -(1/u) du

= ln u = -ln cos x

but sec x = 1/cos x

...?

Edit:

Nvm figured it out -.-

- ln cos x = ln cos x^-1

= ln sec x

so they are equivalent....duh