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Mathematics - Functions Question with Solution | TestHub

MathematicsFunctionsDomain-RangeMedium2 minPYQ_2015
MathematicsMediummultiple choice

Letfx=sinπ6sinπ2sinx, for allxRandgx=π2sinx, for allxR. Letfog xdenotefgxandgof xdenotegfx. Then which of the following is (are) true?

Question diagram: Let f x = sin ⁡ π 6 sin ⁡ π 2 sin ⁡ x , for all x ∈ R and g

Options:(select one or more)

Answer:
A, B, C
Solution:

fx=sinπ6sinπ2sinx
-π2π2sinxπ2
-1sinπ2sinx1
sin-π6sinπ6sinπ2sinxsinπ6
-12sinπ6sinπ2sinx12
fgx=sinπ6sinπ2sinπ2sinx
-1sinπ2sinx1
-π2π2sinπ2sinxπ2
-1sinπ2sinπ2sinx1
-π6π6sinπ2sinπ2sinxπ6
-12sinπ6sinπ2sinπ2sinx12
limx0fxgx=limx0sinπ6sinπ2sinxπ2sinx×π6sinπ2sinxπ6sinπ2sinx

=limx0π6sinπ2sinxπ2sinx=π6.


Range of gfx is π2sin-12,π2sin12
=-π2sin12,π2sin12
Hence, 1, does not belong to this range.

Stream:JEE_ADVSubject:MathematicsTopic:FunctionsSubtopic:Domain-Range
2mℹ️ Source: PYQ_2015

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