Ctg(α - 360⁰) = - Ctg(360⁰ - α) = - Ctgα
tg(- α + 270⁰) = tg(270⁰ - α) = Ctgα
a b c
61х^2+39х+2=0
d = b²-4ac
d = 1521 - 488 = 1033
x = -b+-√d/2a
x1 = -39+√1033/122
x2 = -39-√1033/122