[Au197]

I'm going through an organic chemistry textbook, and I got stuck.

with bond angles, the book says that its trigonal planar, I get that, and I get the 109d Angles, but what I don't understand and isn't mentioned anywhere, is the "Observed angle" of 107.3d what is that, and where did they get that figure from.

[AWK]

trigonal planar, I get that, and I get the 109d

Trigonal planar in idealized case should show an angle of 120d.

"Idealized case" does not take into account, eg.: electronegativity of atoms, repulsions, atractions, and steric effects. 

[Au197]

Ah yeah realised my error, the 109 was for another example I was doing and that was a tetrahedral