Thursday, 1 January 2015

calculus - Find the limit as x approaches 0



$$\lim_{x\to 0} \frac{\sin(3x)}{x+\tan(4x)}$$




I am having trouble with this one.



I know that $\lim_{x\to 0}\frac{\sin(x)}{x} = 1$
and same for the inverse



also $\lim_{x\to 0}\frac{\tan(x)}{x} = 1$



I am able to simplify $\sin(x)$ easily by multiplying by $\frac{3x}{3x}$



I am lost as to what to do next however. I seems like a simple problem (and it probably is) and I also know that the limit of the whole function as $x$ approaches $0$ will be $3/5$.




I am also not allowed to use L'Hospital's rule.



Thanks!


Answer



Write



$$\frac{\sin(3x)}{x+\tan(4x)} = \frac{\sin(3x)/x}{1+\tan(4x)/x} = \frac{3\cdot \sin(3x)/(3x)}{1+4\cdot \tan(4x)/(4x)}$$



See what to do now?



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