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Let \(f(x) = \sin^{-1}x\) and \(g(x) = x - 2\). To define the composite function \(f \circ g\), the largest domain of \(g(x)\) has to be

  • A.\([2, 5]\)
  • B.\([1, 3]\)
  • C.\([0, 2]\)
  • D.\([-1, 3]\)
  • E.\([-3, 3]\)

Answer: B

The largest domain is \([1, 3]\).

\(f(g(x)) = \sin^{-1}(x - 2)\), and \(\sin^{-1}\) is defined only for arguments between \(-1\) and \(1\).

\[ \begin{aligned} -1 &\le x - 2 \le 1 \\ 1 &\le x \le 3 \end{aligned} \]

The interval \([-1, 3]\) or \([-3, 3]\) would let \(x - 2\) fall below \(-1\), and \([2, 5]\) lets it exceed 1, so \(f \circ g\) would be undefined at some points. \([0, 2]\) works but is not the largest such interval.

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