In article <49A8C201.firstname.lastname@example.org>, "Stephen J. Herschkorn" <email@example.com> wrote:
> What is the history of the trick to find the indefinite inteegral of the > secant function? Who first used it, and when?
Which trick? z = tan(x/2)? Inverse gudermannian?
The correspondence predates the invention of the formal integral calculus. The same numbers appeared while compiling tables for the loxodrome and for log(tan(x)). I imagine that after the integral calculus was invented, there was no mystery about int sec(x) dx.