The three concurrent forces acting on the post produce a resultant force of 0. If F2 = 0.5F1, and F1 is to be 90 degrees from F2 as shown, determine the required magnitude F3 expressed in terms of F1 and the angle theta. I am having no troubles finding the magnitude of F3, however, I am having trouble understanding how to get theta. Apparently the angle formed by F1 and F2, plus ninety degress, gives you the answer. However, I'm not seeing the relationship. Help?