Law of Cosines, here we come. In this case, we'll say that *b* = 9 and *c* = 13. That leaves *x* = *a* and *A* = 42°. *a*^{2} = *b*^{2} + *c*^{2} – 2*bc* cos *A*
Substitute in our values and solve. *x*^{2} = 9^{2} + 13^{2} – 2(9)(13) cos(42°)
*x*^{2} ≈ 76.1
*x* ≈ 8.7
That's all, folks. |