At noon, ship A is 100 Kilometers due east of ship B, Ship A is sailing west at 12 k/h, and ship B is sailing S10degrees west at 10k/h. At what time will the ships be nearest each other and what time will the distance be?

(not a right triangle)?

I believe I should start with Law of Cosine
c^2=a^2=b^2-2ab Cos C

Need help setting that equation up and then I assume I would take the differvative.

c^2=100^2-x+(-12t)^2-2(100-x)(-12t) Cos100 ?????