Some trigonometric issue Classic List Threaded 9 messages Open this post in threaded view
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Some trigonometric issue

 Hello, I have a rectangle abcd with known width w and height h. The rectangle is rotated according to the theta angle and becomes ab'c'd'. I can calculate the coordinates of the rotated rectangle. However my knowledge in trigonometry is too weak to find the position of the point p on the y axis. This point is at the intersection of the y-axis and the line passing through the upper side of the rectangle after rotation. Does anyone know how to calculate this? The distance between a and b' can be easily calculated, but from there I am not quite sure how to proceed. -- Sent from: http://forum.openscad.org/_______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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Re: Some trigonometric issue

 I think it is just  length(ab) /  acos(theta)On Fri, 16 Oct 2020 at 11:29, amundsen <[hidden email]> wrote:Hello, I have a rectangle abcd with known width w and height h. The rectangle is rotated according to the theta angle and becomes ab'c'd'. I can calculate the coordinates of the rotated rectangle. However my knowledge in trigonometry is too weak to find the position of the point p on the y axis. This point is at the intersection of the y-axis and the line passing through the upper side of the rectangle after rotation. Does anyone know how to calculate this? The distance between a and b' can be easily calculated, but from there I am not quite sure how to proceed. -- Sent from: http://forum.openscad.org/ _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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Re: Some trigonometric issue

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Re: Some trigonometric issue

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Re: Some trigonometric issue

 In reply to this post by amundsen On 2020-10-16 12:28, amundsen wrote: > I can calculate the coordinates of the rotated rectangle. However my > knowledge in trigonometry is too weak to find the position of the point > p on > the y axis. A general solution is based on 2 points on each line + using determinants, details at: https://en.wikipedia.org/wiki/Line%E2%80%93line_intersection#Given_two_points_on_each_lineSe the formula for (Px,Py) Regards Carsten Arholm _______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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Re: Some trigonometric issue

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