The law of cosines that we can use to find the length of side x is:
[tex]x^2=b^2+c^2-2bccos(\theta)[/tex]
Having in mind that we already know b and c and the angle theta:
[tex]x=\sqrt{18^2+14^2-(2\times18\times14\times cos(30))}=9.1391026[/tex]
Then the right answer is 9.1391.
