[SOLVED] cosine rule help!

I have racked my brain trying to think of what I've done wrong, but I just can't. (Headbang)

**Jim and Tony leave the same point at the same time with Jim walking away at the speed of 1.4m/s and tony at a speed of 1.7m/s, the two directions of travel making a angle of 50 degrees with eachother. If they continue on the same straight line paths how far apart are they after 8 seconds?**

*x^2=6.3^2+7.2^2-2(6.3)(7.2)cos17*

x^2=91.53-90.72Xcos17

x^2=91.53-86.76

x^2=4.77

x=2.18(Angry)

Can someone please help me? I want to know what I've done wrong! and thank you for taking the time to read this post =]

xxx

marika