Projection (linear algebra)
= Projection
{disambiguate=linear algebra}
{title2=$P^2=P$}
{wiki}
= Idempotent linear map
{synonym}
= Linear projection
{synonym}
A <linear projection> is an <idempotent> <linear operator>: $P^2=P$. Every vector decomposes as $x=Px+(I-P)x$, into the <image of a linear map> and the <kernel of a linear map>. Those two <vector subspaces> form a <direct sum>. An <orthogonal projection> additionally uses the <orthogonal complement> in an <inner-product space>.