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The two structural members, one of which is in tension and the other in compression, exert the indicated forces on joint O. Determine the magnitude R of the resultant R of the two forces and the angle θ which R makes with the positive x axis (measured counterclockwise from the x axis).

I have the resultant force but I don't know how to get theta.

problem1

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Do you have the $x$ and $y$ components of the resultant? If so, then just use $\theta=\arctan(y/x)$ –  Omnomnomnom Sep 4 '13 at 3:23
    
My x component is 3.81616. My Y component is -1.07517. When I use arctan(y/x) i get -15.7347. That answer is apparently incorrect. –  R3alAli Sep 4 '13 at 3:45
1  
It could be that they want a positive angle. I'm not sure how many tries you have, but what about $360-15.7347=344.2653$? At any rate, you should definitely get an angle in the lower-right quadrant, so you can't be too far off the right track... –  Omnomnomnom Sep 4 '13 at 3:49
    
You were correct. Thanks for your help. –  R3alAli Sep 4 '13 at 4:05

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