Editing Discrete cosine transform (section)

== Inverse transforms ==
Using the normalization conventions above, the inverse of DCT-I is DCT-I multiplied by 2/(''N''&nbsp;−&nbsp;1). The inverse of DCT-IV is DCT-IV multiplied by 2/''N''. The inverse of DCT-II is DCT-III multiplied by 2/''N'' and vice versa.<ref name="pubRaoYip"/>

Like for the DFT, the normalization factor in front of these transform definitions is merely a convention and differs between treatments. For example, some authors multiply the transforms by <math display="inline">\sqrt{2/N}</math> so that the inverse does not require any additional multiplicative factor. Combined with appropriate factors of {{sqrt|2}} (see above), this can be used to make the transform matrix [[orthogonal matrix|orthogonal]].