Monday, 12 December 2016

limits - Without using Taylor expansion, how do I find the value of K if limxrightarrow0fracx2sin(Kx)xsinx=1

limx0x2sin(Kx)xsinx=1



Here K is a constant whose value I want to find,




I got it by writing the series expansion of sin(θ), but couldn't by L'hospital rule or standard limits,



This is what I tried:



limx0x2sin(Kx)xsinx=1



limx0xsin(Kx)1sinxx=1



limx0Kx2sin(Kx)Kx1sinxx=1



So this gives a 0 in the denominator which doesn't help, L'hospital gives a huge mess, applying it once more didn't help



The answer given is K =1/6.

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