need mathematica coding for this question

Question

12. Determine how large the number b has to be in order that ∫∞to b (1/x^2+1) dx < 0.001

Answer 1

int = Integrate[1/(x^2 + 1), {x, b, Infinity}]

>> 1/2 (Pi - 2 ArcTan[b])

Reduce[int < 1/1000, b]

>> b > Tan[(-1 + 500 Pi)/1000]