How would I find the angle between two lines using trigonometry?

Use the Side Angle Side law I think... I can't remember what the law says but you can Google it. That or use SOHCAHTOA, it should be in your book or online somewhere if you need to know how to do that. Try Purplemath (http://www.purplemath.com) if that dosen't work.

Look at the Sine Rule and Cosine Rule in your text book.