Verified answer

y = arcsin x/6

|x/6| ≤ 1

-6 ≤ x ≤ 6

y = arccos 7x

|7x| ≤ 1

-1/7 ≤ x ≤ 1/7

y = arctg 12x

12x ∈ R

x ∈ R

y = arcctg x/9

x/9 ∈ R

x ∈ R