Final answer:
The magnitude of the resultant force at point A requires more information about the direction of the forces Fb and Fc. Without direction or angle, we cannot accurately determine the resultant force.
Step-by-step explanation:
To determine the magnitude of the resultant force at point A, we would use the principle of superposition, which states that when two or more forces act at a point, the resultant force is the vector sum of these forces. Unfortunately, the information provided does not include directions or the angles at which the forces Fb (890 N) and Fc (440 N) are acting with respect to point A. Therefore, without additional information such as the direction of the forces or whether they are acting along the same line, perpendicular to each other, or at some other angle, it is not possible to calculate the resultant force accurately.
However, if we make an assumption (which should be verified with additional information), such as Fb and Fc acting perpendicular to each other, we would calculate the resultant force using the Pythagorean theorem: FA = √(Fb² + Fc²). Without the correct assumption or further information, we could only give an example result, not the definitive magnitude of the resultant force at A.