Sunday, 16 February 2014

calculus - Not sure how to evaluate limxto0fracsin6xsin2x (without l'Hospital)




lim



I know I can use L'Hospital's but I want to understand this particular explanation. They seem to skip something, and I'm not seeing the connection:




The limit is \frac{6}{2}=3 since \lim_{x\to 0}\frac{\sin(x)}{x}=1


Answer



For x \neq 0 and x close to zero, we have



\frac{\sin 6x}{\sin 2x} = \frac{\sin 6x}{6x} \cdot \frac{6x}{\sin 2x} = 3 \cdot \frac{\sin 6x}{6x} \cdot \frac{2x}{\sin 2x}



See what to do now?


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