Example 1: Draw the free-body diagram of member ABC.

Draw FBD of ABC: Member ABC is supported by a smooth pin at A, and is connected to member BD by a pin connection at B. A closer look at member BD reveals that it is a two-force member. We make this determination as BD is pin connected at two points, and there is no force or couple moment acting at any point along BD. In this case, BD is assumed to be in compression. Now we can proceed to draw the FBD of ABC as shown below.