Tuesday, April 3, 2012

What is limit [(1/sinx) - (1/x)] as x approaches 0

We have to find the value of lim x -->0 [(1/sinx) -
(1/x)]


if we substitute x = 0 we get an indeterminate form
of inf. - inf.


lim x -->0 [(1/sinx) -
(1/x)]


=> lim x -->0 [(x/x*sinx) - (sin
x/x*sin x)]


=> lim x -->0 [(x - sin
x)/x*sinx)]


substitute x = 0, we get the indeterminate form
0/0. This allows us to use l"Hopital's rule and substitute the numerator and the
denominator with their derivatives.


=> lim x
-->0 [(1 - cos x)/(x*cos x + sin x)]


substitute x =
0


=> (1- 1)/(0-0)


again
the indeterminate form 0/0, use l'Hopital's rule
again


=> lim x -->0 [(sin x)/(cos x - x*sin x
+ cos x)]


=> lim x -->0 [(sin x)/(2*cos x -
x*sin x)]


substitute x =
0


=> 0/ 2


=>
0


The value of lim x -->0 [(1/sinx) -
(1/x)] = 0

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