Answer:
=> Apply law of cosine
[tex]c^2=a^2+b^2-2abcos\left(C\right)[/tex]
=> input value
[tex]z^2=6.5^2 + 9.4^2-\left(6.5\right)\left(9.4\right)\left(cos\left(131\right)\right)[/tex]
=> simplify
[tex]z=\sqrt{\left(6.5^2+\:9.4^2\right)-\left(6.5\right)\left(9.4\right)\left(-0.65605902899\right)}[/tex]
=> calulcation
[tex]z=\sqrt{-61.1\cos \left(131^{\circ \:}\right)+130.61},\:z=-\sqrt{-61.1\cos \left(131^{\circ \:}\right)+130.61}[/tex]
=> apply rule: Distance must be greater than 0
which is about 14.51828
