Question

What is tan3x=1 ?

Answer 1

3x=arctan(1)

Answer 2

you take the inverse tan of both sides which leaves you with 3x on the left, then it's just algebra/using your calculator after that

Answer 3

tan(3x)=sin(3x)/cos(3x)=1.
So, sin(3x) = cos(3x). This only happens for pi/4+k*pi, k is any integer.

So, 3x=pi/4+k*pi => x = pi/12+k/3*pi = pi*(1+4k)/12