# What is the orthogonal complement of a subspace?

## What is the orthogonal complement of a subspace?

In the mathematical fields of linear algebra and functional analysis, the orthogonal complement of a subspace W of a vector space V equipped with a bilinear form B is the set W⊥ of all vectors in V that are orthogonal to every vector in W. Informally, it is called the perp, short for perpendicular complement.

Is the orthogonal complement of a subspace a subspace?

So we know that V perp, or the orthogonal complement of V, is a subspace.

What is the complement of a subspace?

In linear algebra, a complement to a subspace of a vector space is another subspace which forms a direct sum. Two such spaces are mutually complementary. , that is: Equivalently, every element of V can be expressed uniquely as a sum of an element of U and an element of W.

### How do you find the orthogonal complement of a column space?

The orthogonal complement of the row space of A is the null space of A, and the orthogonal complement of the column space of A is the null space of AT : (RowA)⊥=NulA ( Row A ) ⊥ = NulA and (ColA)⊥=NulAT ( Col A ) ⊥ = Nul A T . where A=⎡⎢⎣1450−3106−2⎤⎥⎦ A = [ 1 4 5 0 − 3 1 0 6 − 2 ] .

How do you find the orthogonal complement of a matrix?

Theorem N(A) = R(AT )⊥, N(AT ) = R(A)⊥. That is, the nullspace of a matrix is the orthogonal complement of its row space. Proof: The equality Ax = 0 means that the vector x is orthogonal to rows of the matrix A. Therefore N(A) = S⊥, where S is the set of rows of A.

How do you show orthogonal subspaces?

The subspaces N(A),R(AT ) ⊂ Rn and R(A),N(AT ) ⊂ Rm are fundamental subspaces associated to the matrix A. Theorem N(A) = R(AT )⊥, N(AT ) = R(A)⊥. That is, the nullspace of a matrix is the orthogonal complement of its row space. Proof: The equality Ax = 0 means that the vector x is orthogonal to rows of the matrix A.

#### How do you find orthogonal components?

Decomposing a Vector into Components

1. Step 1: Find the projv u.
2. Step 2: Find the orthogonal component. w2 = u – w1
3. Step 3: Write the vector as the sum of two orthogonal vectors. u = w1 + w2
4. Step 1: Find the projv u.
5. Step 2: Find the orthogonal component.
6. Step 3: Write the vector as the sum of two orthogonal vectors.

How do you calculate orthogonal projection?

Example(Orthogonal projection onto a line) Let L = Span { u } be a line in R n and let x be a vector in R n . By the theorem, to find x L we must solve the matrix equation u T uc = u T x , where we regard u as an n × 1 matrix (the column space of this matrix is exactly L ! ).

What is the orthogonal complement of column space?

The nullspace is the orthogonal complement of the row space, and then we see that the row space is the orthogonal complement of the nullspace. Similarly, the left nullspace is the orthogonal complement of the column space.