Are these two integral formulas the same?

[frasifrasi]

In my book, we were give:

int of tanx dx = - ln|cos x| + c

and later I cam across:

int of tanx dx = ln |sec x| + c

--should I use these interchangeably or what?

 

[D H]

What is the relation between $\cos x$ and $\sec x$?

 

[genneth]

$$ln\left(\frac{1}{x}\right) = -ln x \quad \textrm{and} \quad \sec x = \frac{1}{\cos x}$$

So yes, you can use them interchangeably.