Proof: Derivative of Arctangent

[reddevil16carrick]

Thanks! I needed to learn the proof of the "Arc's" and this helped a lot

[juanpablojou]

Very helpful thanks! i was trying to do a proof for integrating 1/ (x^2+a^2) and didn't know how to start, but i got it.

[deccaftw]

that was really helpful, thank you very much!