Valence angle

[raintrek]

I've just been introduced to the valence and dihedral angles, shown here (b),(c) respectively

http://ccl.net/cca/documents/molecular-modeling/img65.gif

I'm seeking clarification that the angle shown in (b) is indeed the valence angle. I've been given confusing information that for a chain of longer than 3, the valence angle IJK is actually represented by

http://www.trekcore.com/angle.JPG
1. The problem statement, all variables and given/known data



2. Relevant equations



3. The attempt at a solution