1)
а) = 2*π/3 +π/4 + 3π/4 = 5π/3
б) Cos(arctg0) = Cos0 = 1
2)
a) Ctgx = -4 б) Ctgx = -1
x = arcCtg(-4) + πk , k ∈ Z x = arcCtg(-1) + π k , k ∈ Z
x = -arctg4 +πk , k ∈Z x = -π/4 + πk , k ∈ Z
3)
a) tgx < 4 б) Ctgx > 1
-π/2 + πk < x < arctg4 +πk , k ∈Z πk < x < π/4 + πk , k ∈ Z