Question: I'm new to LaTeX and I have a question about the LaTeX code (which I have to do for my essay), for the inner product of vectors on an exponential\*,how can I fix the problem that the two vektors k and x have their vectors taht are not parallel . *The vector of k is much higher that the vector in x* ( I use the command \overrightarrow for the vector, and I have also use the \displaystyle for a sum that exist in the same equation).

How can I fix that?

Thanks cheers :)

Answer: 
Actually, X11 is not erased but moved to /opt/X11. 

So, the simplest solution would probably be to manually add the symbolic link from /usr/X11 to /opt/X11: 

```
sudo ln -s /opt/X11 /usr/X11

```
I had the exact same problem with another program that was working prior to upgrading to OS X Yosemite, and then returned the following error subsequent to upgrading:

```
dyld: Library not loaded: /usr/X11/lib/libX11.6.dylib
  Referenced from: /Users/grosbj/LANL/MCNP5/bin/mcnp5
  Reason: image not found
Trace/BPT trap: 5

```

fabianfuchs' suggestion fixed it!:

```
sudo ln -s /opt/X11 /usr/X11

```

Thanks!