
\[\begin{bmatrix}
1 & 0 & 0 \\
0 & cos(\theta) & -sin(\theta) \\
0 & sin(\theta) & cos(\theta)


Or, better still:

\[R_x (\theta)=\begin{bmatrix}
1 & 0 & 0 \\
0 & cos(\theta) & -sin(\theta) \\
0 & sin(\theta) & cos(\theta)

• Yep, that's precisely the mistake I made. Thanks for weighing in! I've got this paper to finish in...I'd rather not think about the deadline, but it really helped to learn about this! It really is fun to learn about LaTex, and it's really helpful in understanding how people write about mathematics in a professional manner! All I can really say is that Stack Exchange is a professional help site. Again, thanks! – user463013 Jan 7 '18 at 9:43
• better \sin and \cos. etc. these shouldn't be entered as if they are representing the multiplication of three variables, which is what will happen if the letters are entered individually. – barbara beeton Jan 7 '18 at 15:19