In a paper says that the limit when [tex]\alpha \to 0[/tex] with [tex]

[alejandrito29]

In a paper says that the limit when $$\alpha \to 0$$ with $$\sigma = \pm 1$$ of:

$$\frac{1}{4 \alpha}(1 + \sigma \sqrt{1 - \frac{8}{l^2} \alpha } )$$

has a well defined limit only when $$\sigma = - 1$$,

¿why??...I don't understand

 

[disregardthat]

Well, calculate the limit for sigma = -1, and see what happens when sigma = 1 (try to calculate it).