Calculating Unknown Forces in a Vector Diagram

[Xiomara]

Homework Statement

Hi, I'm having trouble with my first mechanics assignment and I'd appreciate some help.
So, an object is being pulled using two ropes (Fa and Fb) with a resultant force of 970 N along the x axis. Angle from Fa to the axis is 20 degrees, angle from fb to the axis is 51 degrees. I need to calculate Fa and Fb.

Homework Equations

I think that I need to use either law of sines or cosines but am not sure.
c^2=a^2+b^2-2abcos(c)
sin(A)/a=sin(B)/b=sin(C)/c

The Attempt at a Solution

I made a vector diagram (triangle). I then tried to find F a and b by plugging all my knowns into the law of sines and solving. sin(C)/c=sin(51)/970=8.0118, but when I try to calculate the others based on this I get very small numbers, less than one. What am I doing wrong??

 

[scottdave]

One thing that the problem does not specifically state, is the direction (above or below) the x axis. So think about this. It is being pulled along the x axis. What does this tell you about the y-component of the resultant vector? Intuitively, one vector will be above the x-axis, and the other below the x-axis.