added definition of unit vector x_gc [ci skip]
added definition of unit vector x_gc [ci skip]

DougBurke/astropy,DougBurke/astropy,MSeifert04/astropy,AustereCuriosity/astropy,kelle/astropy,AustereCuriosity/astropy,saimn/astropy,StuartLittlefair/astropy,kelle/astropy,AustereCuriosity/astropy,stargaser/astropy,aleksandr-bakanov/astropy,mhvk/astropy,mhvk/astropy,astropy/astropy,larrybradley/astropy,stargaser/astropy,dhomeier/astropy,joergdietrich/astropy,kelle/astropy,funbaker/astropy,larrybradley/astropy,bsipocz/astropy,StuartLittlefair/astropy,tbabej/astropy,StuartLittlefair/astropy,lpsinger/astropy,StuartLittlefair/astropy,tbabej/astropy,astropy/astropy,tbabej/astropy,pllim/astropy,DougBurke/astropy,joergdietrich/astropy,tbabej/astropy,aleksandr-bakanov/astropy,dhomeier/astropy,mhvk/astropy,larrybradley/astropy,lpsinger/astropy,dhomeier/astropy,stargaser/astropy,dhomeier/astropy,MSeifert04/astropy,DougBurke/astropy,mhvk/astropy,lpsinger/astropy,funbaker/astropy,AustereCuriosity/astropy,larrybradley/astropy,tbabej/astropy,saimn/astropy,AustereCuriosity/astropy,pllim/astropy,pllim/astropy,bsipocz/astropy,funbaker/astropy,MSeifert04/astropy,saimn/astropy,pllim/astropy,bsipocz/astropy,astropy/astropy,MSeifert04/astropy,kelle/astropy,joergdietrich/astropy,aleksandr-bakanov/astropy,joergdietrich/astropy,saimn/astropy,astropy/astropy,lpsinger/astropy,astropy/astropy,mhvk/astropy,funbaker/astropy,kelle/astropy,aleksandr-bakanov/astropy,StuartLittlefair/astropy,dhomeier/astropy,larrybradley/astropy,lpsinger/astropy,bsipocz/astropy,stargaser/astropy,saimn/astropy,joergdietrich/astropy,pllim/astropy