What restriction should be applied to y is equal to tangent x for y is equal to arctan x to be defined?

To define arctan as the inverse of tangent, tangent must be restricted to an interval where it is one-to-one. The standard interval is the open interval (−π/2, π/2), since tangent is undefined at the endpoints. Therefore, restrict the domain to (−π/2, π/2), which is choice B.

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