Find the domain of sin-1 3x

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  1. [-1, 1]
  2. \(\left[\frac{-1}{2} , \frac{1}{2} \right ]\)
  3. \(\left[\frac{-1}{3} , \frac{1}{3} \right ]\)
  4. \(\left[0 , \frac{1}{3} \right ]\)

Answer (Detailed Solution Below)

Option 3 : \(\left[\frac{-1}{3} , \frac{1}{3} \right ]\)
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Detailed Solution

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Concept:

Principal Values of Inverse Trigonometric Functions:

 

Function Domain Range of Principal Value
sin-1 x [-1, 1] [-π/2, π/2]
cos-1 x [-1, 1] [0, π]
csc-1 x R - (-1, 1) [-π/2, π/2] - {0}
sec-1 x R - (-1, 1) [0, π] - {π/2}
tan-1 x R (-π/2, π/2)
cot-1 x R (0, π)


Calculation: 

Let f(x) = sin-1 3x

As we know domain of sin-1 x is x ∈ [-1, 1]

So, -1 ≤ 3x ≤ 1

\(\Rightarrow \rm \frac{-1}{3} \leq x \leq \frac{1}{3}\)

Hence domain of sin-1 3x is \(\left[\frac{-1}{3} , \frac{1}{3} \right ]\)

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