ctg(270-a)/1-tg^2(a-180)ctg^2(360-a)-1/ctg(180+a)=
=-tga/1+tg^2a*ctg^2a-1/ctga=
=-tga/tga*ctga*(1+ctga*tga)-1/ctga=
=-1/2ctga-1/ctga=
=(-1-2)/2ctga=
=-3/2ctga=
=-1,5tga
ctg(270-a)/1-tg^2(a-180)ctg^2(360-a)-1/ctg(180+a)=
=-tga/1+tg^2a*ctg^2a-1/ctga=
=-tga/tga*ctga*(1+ctga*tga)-1/ctga=
=-1/2ctga-1/ctga=
=(-1-2)/2ctga=
=-3/2ctga=
=-1,5tga