The function f(x) is given by f(x)=⎛⎝x2sin(1x),ifx≠00,ifx=0 Which of the following statement(s) is/are true for f(x)?
A
f(x) is continuous at x = 0
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B
f(x) is differentiable at x = 0
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C
f′(0)=0
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D
f(x) is not differentiable at x = 0
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Solution
The correct options are Af(x) is continuous at x = 0 Bf(x) is differentiable at x = 0 Cf′(0)=0 Given that f(x)=⎛⎝x2sin(1x),ifx≠00,ifx=0limx→0x2=0and−1≤sin(1x)≤1−x2≤x2sin(1x)≤x2limx→0−x2≤limx→0x2sin(1x)≤limx→0x2BySandwitchTheorem,limx→0x2sin(1x)=0∴f(x)iscontinuousatx=0.Now,(RHDatx=0)=limx→0+f(x)−f(0)x−0=limh→0+f(0+h)−f(0)0+h−0=limh→0+f(h)−f(0)h=limh→0+(h)2sin(1h)−0h=limh→0+hsin(1h)=0×(anoscillatingnumberbetween−1and1)⇒(RHDatx=0)=0(LHDatx=0)=limx→0−f(x)−f(0)x−0=limh→0−f(0−h)−f(0)0−h−0=limh→0−f(−h)−f(0)−h=limh→0−(−h)2sin(1−h)−0−h=limh→0−hsin(1h)=0×(anoscillatingnumberbetween−1and1)⇒(LHDatx=0)=0∴(LHDatx=0)=(RHDatx=0)So,f(x)isdifferentiableatx=0andf'(0)=0