Wednesday, August 8, 2018

trigonometry - Limit of trigonometric function: $lim_{xto 0} frac {tan2x}x$

Find $\lim_{x\to 0} \frac {\tan2x}x$



I change tan to sin/cos , we have $\lim_{x\to 0} \frac {\sin2x}{x\cos2x}$



Using l'Hopital's rule,




I get $\lim_{x\to 0} \frac {\cos2x}{(x)(-\sin2x)(\cos2x)}$ = $\lim_{x\to 0} -\frac {1}{(x)(\sin2x)}$



I can't proceed with l'Hopital's rule anymore here as I get 1/0.

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