I'm studying Bose Einstein Condensation.
In the book "Huang K Statistical Mechanics 2 edition", page 288, the author gets the following result for the fugacity ($z$) as a function of temperature and specific volume (lambda is the thermal wavelength and small $v$ the specific volume):
I understand how $z$ is equal to 1. I don't understand how can one obtain the last result for the value of $z$ above the critical temperature.