"Prove that the three orthonormal vectorsa,b, andctaken in that order form a right-handed triad if and only if the scalar triple producta.bxc= 1"

All I know is that the 3-tuple (a,b,c) is a right-handed triad ifc=axb, and a left-handed triad ifc=-axb

Also I'm new to these forums, so how do I (if possible) post variables as greek letters and equations that use sigma notation and similar math symbols?