# Limits- using L'hopital's rule

by Jenkz
Tags: lhopital, limits, rule
 P: 59 1. The problem statement, all variables and given/known data Lim tan (x^1/2)/ [x (x+1/2)^1/2 ] x-> 0 3. The attempt at a solution I have attempted to differentiate both the denominator and numerator seperately but this just seems to complicate the whole equations and I still get a limit of 0. I had an idea to square everything, in which case I get a limit of 1. However, I do not think [tan (x^1/2)]^2 = tanx Please help? My friend and I have been trying to work this out. It isn't homework, merely revision and further understanding.
 P: 1,351 You must have made an error while differentiating, the limit is not 0. [tan (x^1/2)]^2 is not the same as tanx. Try $x = \pi$
 P: 59 My mistake, the equation is tan (x^1/2)/ [x (1+1/x)^1/2 ] sorry I'll try your hint, and have another go at differentiating it. Thanks.
Mentor
P: 20,947

## Limits- using L'hopital's rule

 Quote by Jenkz My mistake, the equation is tan (x^1/2)/ [x (x+1/x)^1/2 ]
Minor point - that's not an equation. They're easy to spot because there's one of these- = - in an equation.
 P: 59 @Mark44: okies, noted. I've tried differentiating it again and I get: $$\frac{\frac{sec^{2}\sqrt{x}}{2\sqrt{x}}}{\sqrt{\frac{1}{x}+1}-\frac{1}{2\sqrt{\frac{1}{x}+x}}}$$ But it still doesn't give me a limit. I'm not too sure how to use your hint. As if i let $$\pi=x$$ Doesnt it just mean $$\pi$$ tends towards 0 instead of x ? Confused...

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