Evaluate $\int_0^{\infty} x^2\,e^{-x^2}\,dx$ if it is convergent.
How to determine $\int x^2 e^{-x^2}\mathrm dx$?
How can I use pathauto to generate URLs for deeply nested vocabularies? I am generating breadcrumbs from URL arguments as described .  I have a vocabulary that looks like this:  Arts-> Performing-> Dancing-> Ballet  I want my url to look like this: arts/performing/dancing/ballet  Using the pathauto module, I can do this for taxonomy terms:  [term:parent]/[term:name]   Which, on the Ballet page, gives me the following; not what I want:  dancing/ballet    If I use parents instead of parent,  ([term:parents]/[term:name]); this is close but not quite:  arts-performing-dancing/ballet   How can I get from arts-performing-dancing to arts/performing/dancing? What is the ideal way to handle data pins D+ and D- on a USB power adapter to be compatible with fast charging on devices? How do "and" and "or" act with non-boolean values? The coefficient of kinetic friction can be calculated using $\mu_k = F_k/F_n$. 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What conditions do you require in the model, in order for this to work? Could someone please refer me to a good paper about this? Why can't humans throw objects at bullet speed when the force involved seems so small? The force that propels a bullet should at least be similar in intensity to the force experienced as recoil and the force exerted on the target. But these forces seem really low (the equivalent of a shove).  If all it takes to make a small object achieve bullet speed is the equivalent of a shove, why can't humans throw objects at these speeds? Extracting usernames from the /etc/passwd file How do I take a screenshot on my Mac? What's the easiest way to take a screenshot of my Mac?  I've used Grab.app, but it's a bit annoying just to get a quick screenshot. Is there a faster way?