Orthogonal Subspaces
Two subspaces S_1 and S_2 of R^n are said to be orthogonal if the dot product v_1·v_2=0 for all vectors v_1 in S_1 and all v_2 in S_2.
See also
Dot Product, SubspaceExplore with Wolfram|Alpha
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Cite this as:
Weisstein, Eric W. "Orthogonal Subspaces." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/OrthogonalSubspaces.html