Ctg²x - 2 ctg x - 3 = 0
Ctg²x - 2 ctg x - 3 = 0 замена: ctgx=t t^2-2t-3=0 t1=4 t2=-1 ctgx=4 ctgx=-1 tgx=1/4 tgx=-1 x1=arctg1/4+пn x2=-п/4+пk