Given : f(x)=4x3−6x2cos2a+3xsin2a.sin6a+√ln(2a−a2) then
A
f(x) is not defined at x=12
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B
f′(12)<0
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C
f′(x) is not defined at x=12
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D
f′(12)>0
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Solution
The correct option is Cf′(12)>0 f′(x)=12x2−12xcos2a+3sin2a.sin6a+0 f′(1/2)=124−122cos2a+3sin2a.sin6a =3−6cos2a+1.5(cos4a−cos8a) So, it will alwyas be greater than 0