[[File:diffract.png]]
Figure: The Incident Ray and Diffract Ray Cone at the Edge of a Building
The other unit vectors for the incident and diffracted rays are found as:
:<math> \mathbf{ \hat{u}_f = \frac{\hat{k} \times \hat{t}}{|\hat{k} \times \hat{t}|} } </math>Â :<math> \mathbf{ \hat{u}_b = \hat{k} \times \hat{u}_f } </math>Â :<math> \mathbf{ \hat{u}_f' = \frac{\hat{k}' \times \hat{t}}{|\hat{k}' \times \hat{t}|} } </math>Â :<math> \mathbf{ \hat{u}_b' = \hat{k}' \times \hat{u}_f' } </math><!--[[File:frml9.png]]-->
The diffraction coefficients are calculated in the following way: