Hi,(adsbygoogle = window.adsbygoogle || []).push({});

I found on youtube a video showing the steps to differentiate tan(x). I can follow the steps quiet easily but I'm not sure which rule is being used when substituting u for cos(x) and du for sin(x)dx.

So which rule is being used and how do I know which is u and which is du.

Thanks

**Physics Forums | Science Articles, Homework Help, Discussion**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Rule for differentiating tan(x)

**Physics Forums | Science Articles, Homework Help, Discussion**