Christian Rau
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 Jan 27 revised Finding the radius of a particular center voxel in 3D cylinder-like structure added 3 characters in body Jan 27 revised Finding the radius of a particular center voxel in 3D cylinder-like structure added 643 characters in body Jan 27 revised Finding the radius of a particular center voxel in 3D cylinder-like structure added 643 characters in body Jan 27 revised Finding the radius of a particular center voxel in 3D cylinder-like structure added 3 characters in body Jan 27 answered Finding the radius of a particular center voxel in 3D cylinder-like structure Jan 27 comment Finding the radius of a particular center voxel in 3D cylinder-like structure @RahulNarain When he says "circle at a perpendicular angle", he probebly means perpedicular to the curve's tangent vector. Jan 25 revised Factorize a Symmetric matrix as an 'Approximation' with an outer product. adjusted formatting Jan 25 suggested approved edit on Factorize a Symmetric matrix as an 'Approximation' with an outer product. Jan 24 suggested rejected edit on How to Determine an Equation of a Circle using a Line and Two Points on a Circle Jan 18 revised Orthogonal matrices, scalar products, projection of a line on a plane added 38 characters in body Jan 18 revised Orthogonal matrices, scalar products, projection of a line on a plane deleted 1 characters in body Jan 18 answered Orthogonal matrices, scalar products, projection of a line on a plane Jan 17 revised Divide a Set of Points along a Direction added 149 characters in body Jan 17 answered Divide a Set of Points along a Direction Dec 9 comment Matrices for which $\mathbf{A}^{-1}=-\mathbf{A}$ @HenningMakholm He just means that a matrix with the searched property can be constructed from any reflection matrix. Though his last paragraph is a bit obsolete, but +1 for the first paragraph. Dec 9 awarded Scholar Dec 9 accepted Matrices for which $\mathbf{A}^{-1}=-\mathbf{A}$ Dec 9 comment Matrices for which $\mathbf{A}^{-1}=-\mathbf{A}$ Ah, ok. Now I understand what you mean by conjugation. And I understand why this keeps the mentioned property but destroys the unitarity property. Thanks again. Dec 9 comment Matrices for which $\mathbf{A}^{-1}=-\mathbf{A}$ I just cannot get what conjugation by a unitary matrix means. I guess with conjugation you mean not just the simple complex conjugate of the matrix elements? Sorry, but I'm not that deeply versed in linear algebra, especially if it gets too theoretical. Dec 9 comment Matrices for which $\mathbf{A}^{-1}=-\mathbf{A}$ Thanks for your answer, but I have difficulties to understand the last sentence. What do you mean with "by conjugating by a non-unitary matrix". Now I understand that it is invariant under conjugation. But aren't the skew-Hermitian and unitary properties invariant under conjugation, too? I don't know how cojugation helps with constructing a counter-example. Or do you mean something different (I don't really understand what conjugation by a non-unitary matrix means)?