tg(x-y) = (tg(x) - tg(y))/(1 + tg(x)·tg(y))
tg(pi/3 - arctg 1/3) = ( tg(pi/3) - tg(arctg 1/3)) / ( 1 + tg (pi/3)* tg(arctg 1/3))= (√3 -1/3)/(1+√3*1/3)=(3√3-1)/(3+√3) это арктангенс
tg (arcctg x)= 1/ ctg(arcctg x)=1/x x<>0
tg(pi/3 - arcсtg 1/3) = ( tg(pi/3) - tg(arcсtg 1/3)) / ( 1 + tg (pi/3)* tg(arctg 1/3))= (√3 -3)/(1+√3*3)=(√3-3)/(1+3√3) это арккотангенс