How do you represent vectors in a 3D space?

[phy-79]

I have problems in understanding what RECIPROCAL VECTORS are...
I know the formulas regarding it but don't know their geometric meaning is...
How do you represent them in a 3D spcace ?

 

[berkeman]

I have problems in understanding what RECIPROCAL VECTORS are...
I know the formulas regarding it but don't know their geometric meaning is...
How do you represent them in a 3D spcace ?

Moved to Homework Help, Advanced Physics for now. Could you please say more about what you know about "reciprocal vectors"?