https://docs.oracle.com/cd/E88353_01/html/E37846/clogl-3m.html
clogl - man pages section 3: Extended Library Functions, Volume 2
clog , clogf , clogl - complex natural logarithm functions These functions compute the complex natural (base e ) logarithm of z , with a branch cut along the...
man pagesextended librarysectionfunctionsvolume
https://manpages.ubuntu.com/manpages/trusty/man3/clog.3.html
Ubuntu Manpage: clog, clogf, clogl - natural logarithm of a complex number
natural logarithm of a complex number
natural logarithmubuntumanpageclog