Test:351 QNo:41

The function f(x)=(x-sinx)/x3 is continuous at x=0, then f(0) is

3 Answers

1
Saket Shukla ·

The explanation to the above question has been given as :
lim(x→0)f(x)=f(0)

Applying LH rule (1-cosx)/2x2=sin2(x/2)/x2=1/4

However I solved it in the following way:

Applying LH rule 3 times= (1-cosx)/3x2= sinx/6x=cosx/6

hence lim(x→0)cosx/6=1/6

Could you please tell me what's wrong in this?

11
Mani Pal Singh ·

This have to done by the following method
Use the expansion of Sin x =x-x3/3!..........

=+1/6

so ur answer is correct

1357
Manish Shankar ·

you are absolutely right saket

there is a mistake in the solution
Applying LH rule (1-cosx)/2x2=sin2(x/2)/x2=1/4
instead of this it should have been
Applying LH rule (1-cosx)/3x2=2sin2(x/2)/3x2=1/6

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