When three coplanar and non-parallel forces are in equilibrium, I. they can be represented in magnitude and direction by the three sides of a triangle taken...

Answer Details

When three coplanar and non-parallel forces are in equilibrium, there are certain properties that hold:
I. The three forces can be represented in magnitude and direction by the three sides of a triangle taken in order. This is known as the triangle of forces.
II. The lines of action of the three forces meet at a point. This point is called the point of concurrency.
III. The magnitude of any one force is equal to the magnitude of the resultant of the other two.
IV. Any one force is the equilibrant of the other two.

Therefore, the correct statements are:
I & II are always true for any three coplanar non-parallel forces in equilibrium.
III is true because the resultant of two forces is equal in magnitude and opposite in direction to the third force.
IV is also true because the equilibrant of two forces is equal in magnitude and opposite in direction to the third force.
Therefore, the correct answer is:
I, II, III & IV.