NOTE: THIS DOCUMENT IS OBSOLETE, PLEASE CHECK THE NEW VERSION: "Mathematics of the Discrete Fourier Transform (DFT), with Audio Applications --- Second Edition", by Julius O. Smith III, W3K Publishing, 2007, ISBN 978-0-9745607-4-8. - Copyright © 2017-09-28 by Julius O. Smith III - Center for Computer Research in Music and Acoustics (CCRMA), Stanford University
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Orthogonality
The vectors (signals)
and
are said to be orthogonal if
, denoted
. That is to say
Note that if
and
are real and orthogonal, the cosine of the angle between them is zero. In plane geometry (
), the angle between twoperpendicular lines is
, and
, as expected. More generally, orthogonality corresponds to the fact that two vectors in
-space intersect at a right angle and are thus perpendiculargeometrically.
Example (
):
Let
and
, as shown in Fig. 6.8.
The inner product is
. This shows that the vectors are orthogonal. As marked in the figure, the lines intersect at a right angle and are therefore perpendicular.