1.1.17
The resultant of the plane system of convergent forces F1, F2, F3 and F4 is zero.
Determine the modulus of force F1 if the projections of three other forces on the coordinate axes are known: F2x =
4H, F2y = 7H, F3x = -5H, F3y = -5H, F4x = -2H, F4y = 0. (Answer 3.61)