Question Details

The Range of f(x) = sin-1 ( 1 x2 - 2x + 2 ) is

Options

A

( 0, π2 )

B

[ 0, π2 ]

C

( 0, π2 ]

D

[ 0, π2 )

Show Answer

Correct Answer :

Option C

( 0, π2 ]

Solution :

The correct option is:

( 0 , π 2 ]

To find the range of the function f ( x ) = sin - 1 ( 1 x 2 - 2 x + 2 ) , we first analyze the expression inside the inverse sine function.

Let g ( x ) = x 2 - 2 x + 2 .
We can rewrite this quadratic expression by completing the square:
g ( x ) = ( x - 1 ) 2 + 1

Since the square of any real number is non-negative, we have:
( x - 1 ) 2 0
Adding 1 to both sides:
g ( x ) 1

Thus, the range of g ( x ) is [ 1 , ) .

Now, we look at the reciprocal term inside the sin - 1 :
Let y = 1 g ( x ) = 1 ( x - 1 ) 2 + 1

Since 1 ( x - 1 ) 2 + 1 < , taking the reciprocal reverses the inequality:
0 < 1 ( x - 1 ) 2 + 1 1
This means the argument y lies in the interval ( 0 , 1 ] .

Since the function sin - 1 ( y ) is strictly increasing for y [ - 1 , 1 ] , we can apply the inverse sine to the bounds of the interval:
As y 0 + , sin - 1 ( y ) 0 .
For the upper bound, when y = 1 , sin - 1 ( 1 ) = π 2 .

Therefore, the range of the function is:
( 0 , π 2 ]

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