Law of Cosine formula not working

[BB_14100646]

I'm using MathCAD 9.0.0.0. I'm not sure why I'm getting the wrong answer. The calculation should be...

R = 329.687 N

...but I'm getting...

R = 108695.156 N

Is there something wrong with my settings?

Thanks,

    Brent 

[Werner_E · Accepted solution]

Law of cosine is R²=P²+... and NOT R=P²+...

So you have to use the square root to get R

[BB_14100646]

Thank you again!!!!