If f∘g(x)= and g∘f(x)=∣sinx∣, then

If f∘g(x)= √x and g∘f(x)=∣sinx∣, then

  1. A.

    f and g cannot be determined

  2. B.

    f(x)=sin x

  3. C.

    f(x)=x2, g(x)=sin x

  4. D.

    f(x)=(x),g(x)=√x​

Attempted by 68 students.

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Correct answer: A

(a)

Given Conditions:

        1.)    (f g) (x) = x

f(g(x)) =x (Equation 1)

        2.)    (g f) (x) = sin x

                ⇒g(f(x)) = sin x (Equation 2)

 

Checking the Given Options:

Option (D): f(x)=x, g(x)=x

-> ​Compute f(g(x)) : f(g(x)) = f(x) = x

o   Satisfies f g(x)= x (Equation 1)

-> Compute g(f(x)): g(f(x)) = g(x) = x

o   This must equal sin x, but x ≠ ∣sin x in general.

o   Does not satisfy Equation 2.

               Conclusion: Incorrect.

 

Option (B): f(x)=sin x

->Compute f(g(x)):  f(g(x)) = sin(g(x))

o   For this to be x ​, we would need sin(g(x)) = x​, which isn't a general identity.

o   Does not satisfy Equation 1.

->Compute g(f(x)): g(f(x)) = g(sin x)

o   If g(x)=x, then g(f(x)) = sin x, which satisfies Equation 2.

But since f(g(x)) = sin(g(x)) ≠ x, this option is incorrect.

 

Option (C): f(x) = x2, g(x)=sin x

->Compute f(g(x)):

o   f(g(x)) = f(sin x)=(sin x)2

o   This must equal x​, but (sin x)2 does not match x​ in general.

o   Does not satisfy Equation 1.

-> Compute g(f(x)): g(f(x)) = g(x2) = sin(x2)

o   This must equal sin x, but sin(x2) ≠ ∣sin x in general.

o   Does not satisfy Equation 2.

Conclusion: Incorrect.

 

Option (A): f and g cannot be determined.

->Since none of the options satisfy both conditions simultaneously, we cannot determine explicit functions f(x) and g(x) from the given choices.

 

Correct Answer: (A) f and g cannot be determined.

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