Recent content by pkleinod

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    Drawing Protein Helix with Twists and Curves: How to Proceed?

    Hello. The attachment contains a sketch of how to proceed. The equations have not yet been checked numerically, so use with caution.
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    Is it possible to rotate circles in 3D using coordinates and normals?

    Hello Otis and welcome to PF. It is not clear to me exactly what you want to do. At first sight, it would seem to me that any point within the original circle would still be inside the rotated circle. Obviously, I have not understood what you want. However, if CG means computer graphics, then...
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    Classical Works on Physics, online?

    I would love to know the answer to this question too. There is probably not much available for free. You might try the Gutenberg project http://www.gutenberg.org/catalog/world A search for "physics" returns some things by Einstein and something by Poincare.
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    Finding the Area of a Parallelogram with Two Vectors in R^4

    Ah! That's the spirit! Does the wedge product ever fail? ' "No, never." "What, never?" "Well, hardly ever!" ' (G&S: HMS Pinafore) To tickle your curiosity: In the 5-dimensional conformal model of Euclidean 3D space, the expression for a sphere in terms of 4 vectors (in...
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    Finding the Area of a Parallelogram with Two Vectors in R^4

    Yes, that is fine, but here is another, more direct, way to get the area by calculating the magnitude of the bivector representing the parallelogram. In terms of a set of orthonormal basis vectors \{ e_i }, i = 1,N \} in N dimensions. The vectors are \vec{a} = \sum_i a_i e_i...
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    Rotating vectors and matrices

    Hello and welcome to PF! To rotate one vector into another one, you need only a single rotation in the plane containing the two vectors. Here is a general method of finding such a single rotation. The angle of rotation is a bivector whose direction specifies the plane of rotation and...
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    Recipe for preparing electrolyte

    To get you started, here is a link to a PhD thesis devoted to this topic. http://deposit.ddb.de/cgi-bin/dokserv?idn=969279493&dok_var=d1&dok_ext=pdf&filename=969279493.pdf
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    Mathematica Explain why chords sound pleasant mathematically?

    Yes, and there are some intervals that can sound both pleasant or unpleasant depending on the context. The interval C to G#, an augmented fifth, is dissonant, whereas C to A-flat, a minor sixth, is consonant. This is so even on a piano, where these intervals are exactly the same. To hear...
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    Finding the face of an icosahedron in which a vector falls in

    Hmmm. Does this really work? Consider a point on the sphere whose vector is perpendicular to one of the faces (i.e. the reference vector for the face, as defined in my post above). The projection of this vector onto its face would be zero, whereas the projection onto the other faces (excluding...
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    Finding the face of an icosahedron in which a vector falls in

    Oops. I meant the LARGEST dot product.
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    Finding the face of an icosahedron in which a vector falls in

    Welcome to PF! Never having done such a calculation, I am not sure of my ground here, but since no one else has yet replied, here is a suggestion that might work: Let a, b, and c be unit vectors (relative to an origin at the centre of the sphere) representing the vertices of one of the...
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    Factoring a wedge product into vectors? (geometric algebra)

    You would probably always use a Euclidean metric because the outer product factorization should not be dependent on the metric. I vaguely recall seeing this somewhere else in the book (probably in dealing with the meet and the join). Glad you like the book---I'm sure it will be a valuable asset.
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    Factoring a wedge product into vectors? (geometric algebra)

    Algorithm for factoring a blade (from Dorst et al. GA4CS p. 535): 1. Input is a non-zero blade B of grade k. 2. Determine the norm s =||B|| 3. Represent the blade in a basis and then find the basis blade E in this representation with the largest coordinate; now you have a list of k basis...
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    About polar vectors and pseudo vectors

    As we did not own a car, my mother was fond of referring to her wash machine as our "pseudo-automobile" because it was not a car but had four wheels. My baby brother grew up speaking in this way and became a Great Physicist, since he grasped the notion of pseudovector at once: it is not a...
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    Geometrical algebra's: simple equation

    On the contrary, it means that k lies in the subspace F, and this implies that F can be factored as F=k\wedge a, where a is some vector. i.e. F is not only a bivector but is also a blade. Then k\wedge F = k\wedge k\wedge a = 0 . (Recall that, in 4 dimensions, a bivector does not in...
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