# Hybridization theory (orbitals used in different hybridizations)

Why is $$d_{x²-y²}$$ orbital used in $$sp^3d$$ (square pyramidal geometry) while $$d_{z^2}$$ orbital in $$sp^3d$$ (trigonal bipyramidal geometry)? I came across this information while reading J.D.Lee Concise inorganic chemistry.