• Title: Orthogonal Complement

  • Series: Hilbert Spaces

  • Chapter: Orthogonality

  • YouTube-Title: Hilbert Spaces 6 | Orthogonal Complement

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  • Subtitle on GitHub: hs06_sub_eng.srt missing

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  • Definitions in the video: orthogonal complement, orthogonality

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  • Quiz Content

    Q1: Let $X$ be a Hilbert space and $x,y \in X$ linearly dependent. What is a correct implication?

    A1: If $x,y$ are orthogonal, then at least one of the two vectors is the zero vector.

    A2: If $x,y$ are orthogonal, then both vectors are given by the zero vector.

    A3: If $x,y$ are orthogonal, then $x = y$.

    A4: If $x,y$ are orthogonal, then $\langle x, y \rangle \neq 0$.

    Q2: Let $X$ be a Hilbert space and $A,B \subseteq X$ be two subsets. What does it mean that $A$ is orthogonal to $B$?

    A1: $\langle x, y \rangle = 0$ for all $x \in A$ and $y \in B$.

    A2: $\langle x, y \rangle \neq 0$ for all $x \in A$ and $y \in B$.

    A3: $\langle x, y \rangle = 1$ for all $x \in A$ and $y \in B$.

    A4: $\langle x, y \rangle = 1$ for all $x \in A$ and and one $y \in B$.

    Q3: Let $X$ be a Hilbert space and $B \subseteq X$ be a subset. What is in general not correct for the orthogonal complement $B^\perp$?

    A1: $B^\perp$ is an open subspace in $X$.

    A2: $B^\perp$ is a subspace of $X$.

    A3: $B^\perp$ is a closed set in $X$.

    A4: $B^\perp = (\overline{\mathrm{Span}(B)})^\perp$.

    A5: $\overline{B^\perp} = (\overline{B})^\perp$.

  • Date of video: 2024-10-17

  • Last update: 2026-02

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