https://www.physicsforums.com/threads/derivative-of-1-x.211489/ In the last post, three last steps. He changes -h into -1, how does this work? I know that if you for example have h/h it's equal to 1 regardless of what value h has, since they're both the same value. I don't see that being applied here though. Could anyone help me out? By the way, i tried messaging the person who posted it, but he is no longer active on this forum. The thread is also not open for further replies.