If two or more than two forces are acting on a single point then the forces are known as system of concurrent forces and if they are acting on a single plane then the forces are called as coplanar forces. Copy the link given below and paste it in new browser window to get more information on Lami's Theorem:- http://www.transtutors.com/homework-help/mechanical-engineering/force-systems-and-analysis/lamis-theorem-solved-examples.aspx

2.  Introduction
 Coplanar Concurrent System of Forces
 Lami’s Theorem
 Examples

3.  Coplanar and non-coplanar forces
 Collinear and non-collinear forces
 Concurrent and non-concurrent forces
 Parallel and non-parallel forces

4.  Coplanar System - The line of action of all the forces lie on a single
plane.
 Concurrent System - The line of action of all the forces intersect at a
common point.

5. If three coplanar forces simultaneously acting at a point are in equilibrium
then each force is proportional to the sine angle of the other two forces.
Consider the forces A, B and C as shown in figure.

6. Determine the tension in the strings that support a lamp fixture as shown
in figure.

7. Determine A string ABCDE whose one end A is fixed to the wall and the
other end E is loaded with a weight of 300N. The string passes through a
frictionless pulley and other two weights are hung at B and C as shown in
figure. Determine the tension in the string and the magnitude of weights
W1 and W2.

8. This was just a summary on Lamis Theorem. For more detailed information
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