Solving a Law of Cosines Problem: Finding the Length of a Side

[themadhatter1]

Homework Statement

[PLAIN]http://img28.imageshack.us/img28/1046/mathproblemp.jpg

Homework Equations

Law of Cosines

The Attempt at a Solution

I'm not really sure what to do for this problem, it looks easy but I can't figure it out. I tried # 11 and was able to find d.

d²=a²+b²-2(a)(b)cos(30)
d=3.23

However, I don't know where to go from there.

 

[vela]

Hints:

1. What do you know about the angles of the opposite corners of a parallelogram?
2. What do you know about the sum of the angles of a parallelogram?

 

[themadhatter1]

Ahh... thanks, I didn't know the basic properties of parallelograms. Now this problem is much easier.