I am trying to run a software (HTML based) and when Tomcat runs to open it, I get the following messages:    The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: /usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib   And this:  Apr 17, 2015 2:13:58 AM org.apache.catalina.core.StandardContext startInternal SEVERE: Error listenerStart   I have tried a lot of things, no solution so far.    The error seems to appear several times. This is part of the LOG:     INFO: Deploying configuration descriptor /opt/OpenForisCalc/calc-server/tomcat/conf/Catalina/localhost/calc.xml       Apr 17, 2015 2:13:58 AM org.apache.catalina.core.StandardContext startInternal    SEVERE: Error listenerStart      Apr 17, 2015 2:13:58 AM org.apache.catalina.util.SessionIdGenerator createSecureRandom    INFO: Creation of SecureRandom instance for session ID generation using [SHA1PRNG] took [208] milliseconds.      Apr 17, 2015 2:13:58 AM org.apache.catalina.core.StandardContext startInternal    SEVERE: Context [/calc] startup failed due to previous errors    Apr 17, 2015 2:13:58 AM org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc       SEVERE: The web application [/calc] registered the JDBC driver [org.postgresql.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
Trying to run , embedded Tomcat instance fails.  Error seems to appear here:    Apr 17, 2015 2:13:47 AM org.apache.catalina.startup.HostConfig deployDescriptor  INFO: Deploying configuration descriptor /opt/OpenForisCalc/calc-server/tomcat/conf/Catalina/localhost/calc.xml  Apr 17, 2015 2:13:58 AM org.apache.catalina.core.StandardContext startInternal   SEVERE: Error listenerStart   Then if messes up with the rest (this repeats a lot):  Apr 17, 2015 2:13:58 AM org.apache.catalina.core.StandardContext startInternal  SEVERE: Context [/calc] startup failed due to previous errors
Combinatorial argument for $\sum\limits_{k=i}^{n}\binom{n}{k}\binom{k}{i} = \binom{n}{i}2^{n-i}$ I need to show that $$\sum\limits_{k=i}^{n}\binom{n}{k}\binom{k}{i} = \binom{n}{i}2^{n-i}$$  I know that $\displaystyle \binom{n}{k}\binom{k}{i}$ is counting the number of ways to pick $k$ elements from $n$ and then $i$ elements from those $k$, so $\displaystyle \sum\limits_{k=i}^{n}\binom{n}{k}\binom{k}{i}$ is counting the number of ways to do that $\forall k$.  I know that $\displaystyle \binom{n}{i} = \binom{n}{n-i}$ and that $2^{n-i}$ is the number of elements in the power set for $[n]\setminus[i]$.  How do I show that both sides are equivalent? I'm stumped on this one. Could anyone give me a pointer in the right direction? I'm having this Error when I try to compile my .tex file with xelatex:  ! Package hyperref Error: Wrong DVI mode driver option `dvips', (hyperref)                because XeTeX is running.  See the hyperref package documentation for explanation.   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I start with knowing that two numbers are coprime if:  $n*k + m*j = 1$  So, setting $k = a$ and j = $a+1$ I can solve as follows:  $n*a + m*a + a$  Then,  $a(n+m) + m = 1$  Where can I go from here? Where do AirDrop files go when I transfer them between an iPad, iPhone and iPod? I AirDropped some Google Docs from my iPad to my iPhone but nothing happened; where did my files go? The file was a list of tools. I don't know much about this,  But I've some of the questions on which some user has answered (not helpful answer) also but I want to delete those questions, but whenever I go to delete that question. It is prompting with     What does it mean? Can someone tell me what would be the action taken by Stack Exchange if I delete more questions? Emacs: Symbol's value as variable is void Let $A,B \subset \mathbb{R}$. 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How can I get a point on that polyline from end points specified by the given distance.    How can I get this by using arcpy provided that this script should work on ArcView without importing any modules (). I'm trying not to hard code values.  Related Question: Indefinite integral $\int(\sin x)^2/(x\cdot\cos x-\sin x)^2\,dx$ How to find the antiderivative of $\dfrac{(\sin x)^2}{(x\cdot\cos x-\sin x)^2}$? I know that series theory can solve the problem. But I wish to solve the problem by the antiderivative way. The numerator and denominator divide the $x^2$ at the same time, don't they? How do I tell if ACR will work with my camera and how do I get the correct version for Photoshop?