h09gudef.gif (1287 bytes)

h09gude.gif (1569 bytes)The gudermannian is a combination of a tangent and the exponential function. We see often a supplementary factor 2 and constant - π/2.

The inverse of the gudermannian function can be written as a combination of the natural logarithm, the secant and the tangent:

gd-1(x) = ln (sec(x) + tan(x))