JEE-Advanced 2015 (17/40)

Geometry Level 3

For real x x , define f ( x ) = sin ( π 6 sin ( π 2 sin x ) ) f(x)=\sin \left( \frac{\pi}{6} \sin \left( \frac{\pi}{2} \sin x \right) \right) and g ( x ) = π 2 sin x g(x)=\frac{\pi}{2} \sin x . Let ( f o g ) ( x ) (fog)(x) denotes f ( g ( x ) ) f(g(x)) and ( g o f ) ( x ) (gof)(x) denotes g ( f ( x ) ) g(f(x)) . Then which of the following is/are true?

( 1 ) The range of f is [ 1 2 , 1 2 ] ( 2 ) The range of f g is [ 1 2 , 1 2 ] ( 3 ) lim x 0 f ( x ) g ( x ) = π 6 ( 4 ) There is an x R such that f g ( x ) = 1 \begin{array} { r l } (1) & \text{ The range of }f \text{ is } [-\tfrac12, \tfrac12] \\ (2) & \text{ The range of } f\circ g \text{ is } [-\frac12, \frac12 ] \\ (3) & \lim \limits_{x\to0} \frac{f(x)}{g(x)} = \frac\pi6 \\ (4) & \text{ There is an }x\in\mathbb R \text{ such that } f \circ g (x) = 1 \end{array}

Submit your answer as the increasing order of the serial numbers of all the correct options. For example, if your answer is ( 1 ) , ( 2 ) (1),(2) , then submit 12 as the correct answer, if your answer is ( 2 ) , ( 3 ) , ( 4 ) (2),(3),(4) , then submit 234 as the correct answer.


The answer is 123.

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