A Physics question with Trig...

Hi

I'm stumped on a physics question here, which goes:

**The vector, v, has the following components: Vx= +65.0 m/s , Vy= -120 m/s**

Calculate the magnitude and polar positive direction of the vector, v.

(Sorry, but please assume the "v" as the v with an arrow over it, and the x and y in Vx and Vy as subscripts...)

So, using that information, I graphed out a triangle and found the hypotenuse.

http://imgur.com/rnpjg.jpg

To get the polar positive direction, I believe I need the degree of the angle that the red arrow is pointing to. But how do I find that angle?

I've tried using tan=opp/adj, or tan=Vy/Vx, but I get a negative number as my answer. Could somebody please help me with this question?

Thanks a lot.

(Also, am I right in thinking that the hypotenuse is the magnitude of the vector?)