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 Apr20 answered Find the sum of the roots of a quadratic function given the vertex of its graph Apr16 comment Laplace's equation in Polar coordinate, an example? The above is not an equation but an expression. Apr14 revised Non-existing Limit of $\sin x$ edited title Apr14 comment Non-existing Limit of $\sin x$ by $sinx$ did you mean $\sin(x)$? Apr13 comment Intersection of two circular arcs with same center Without a description of how Azimuth is measured the question is not well defined. Apr12 revised Distance between two rectangulars added 103 characters in body Apr12 comment Distance between two rectangulars Getting the minimum distance between a point and a line is easy. Getting the minimum distance between a point and a line segment is much harder to do right. You have to account for the ends and see if the minimum point falls outside the segment, and on which side. Apr12 answered Distance between two rectangulars Apr12 revised Some proprieties of the matrix $A^\top A$ added 4 characters in body; edited title Apr12 comment Some proprieties of the matrix $A^\top A$ Use ^\top for transposes. Apr9 comment Calculating the length of the semi-major axis from the general equation of an ellipse Note: Use math.stackexchange.com/a/785054/3301 to find the center. Apr9 comment Calculating the length of the semi-major axis from the general equation of an ellipse Just as I decided to write this exact answer you beat me to it. Apr7 revised How do I prove that $\arccos(x) + \arccos(-x)=\pi$ when $x \in [-1,1]$? roman formatting of sines and cosines Apr2 answered Normal Vector of plane for Rotation Apr2 revised Normal Vector of plane for Rotation Removed unnecessary text and code formatted expressions Apr1 answered Matrix multiplication with transpose Mar31 answered Parametric representation of a plane cut of a sphere at y=5 Mar31 comment Parametric representation of a plane cut of a sphere at y=5 Do you want a tangent plane at the surface of the sphere? A plane cuts a sphere into a circle. You want the equation for the circle when $y=5$? (BTW $y=5$ is a representation for a plane). A general plane has equation $Ax+By+Cz+D=0$. Mar23 comment Geometry: Find angle x in triangle Can you confirm the AB=CD statement? Mar23 comment Shifting RGB colors based on ratio Convert RGB into HSV and compare the V values.