Domain of function/Summer HW?

Question

Hey does anyone know the domain to the following examples??

1) y=squarerooot(x-3)-
squareroot(x+3)
2) y=squareroot[tan(x)]

I tried looking at the graphs on the calculator but I am a little confused

Answer 1

1) the number under the sqrt must be >=0
so x-3>=0 implies x>=3 which also covers x+3>=0
tanx>=0 so 0<=x