A supporting hyperplane of a set is a hyperplane
through a boundary point of
such that
lies entirely in one of its closed half-spaces. More precisely, if
is a boundary point and
is a nonzero vector with
for
every
,
then
is a supporting hyperplane at . The symbol
denotes the dot product
(Boyd and Vandenberghe 2004, pp. 50-51).
In three dimensions, a supporting hyperplane is a supporting plane. Every boundary point of a nonempty set that is a convex set has a supporting hyperplane, but the supporting hyperplane need not be unique (Boyd and Vandenberghe 2004, p. 51).