-- find the horizontal and vertical components of F1.
-- find the horizontal and vertical components of F2.
-- find the horizontal and vertical components of F3.
-- add up the 3 horizontal components; their sum is the horizontal component of the resultant.
-- add up the 3 vertical components; their sum is the vertical component of the resultant.
-- the magnitude of the resultant is the square root of (vertical component^2 + horizontal component^2)
-- the direction of the resultant is the angle whose tangent is (vertical component/horizontal component), starting from the positive x-direction.
