A) \[3(x-1)\cos (3x+4)+\sin (3x+4)\]
B) \[(b-1)\sin (3x+4)+3\cos (3x+4)\]
C) \[(b-1)\cos (3x+4)+3\sin (3x+4)\]
D) None of these
Correct Answer: A
Solution :
Area bounded by the curve \[y=f(x),\,\]x-axis and the ordinates \[x=1\] and \[x=b\] is \[\int_{1}^{b}{f(x)\,dx}\] \ From the question \[\int_{1}^{b}{f(x)\,dx=(b-1)\sin (3b+4)}\] Differentiate with respect to b, we get \[f(b)\,.\,1=3(b-1)\cos (3b+4)+\sin (3b+4)\] \[f(x)=3(x-1)\cos (3x+4)+\sin (3x+4)\].You need to login to perform this action.
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