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Started programming on a ZX spectrum in the 80's and have moved through Assembly, Turbo Pascal, C++, C#, Fortran. My main area of focus is engineering and scientific computing like numerical methods and 3D graphics.


Sep
10
comment O.D.E of the form $dy/dt=f(y)$
Note that $$\int {\rm d}t = \int \frac{1}{y^2 (4-y^2)}\,{\rm d}y$$
Sep
10
revised O.D.E of the form $dy/dt=f(y)$
added 12 characters in body
Sep
10
comment Parabola - equation from three points
possible duplicate of How to find a generic parabola through 3 arbitrary points in R^2?
Sep
10
comment Parabola - equation from three points
Related question: math.stackexchange.com/q/889569/3301
Sep
10
comment Parabola - equation from three points
What is easier than posting on Mathematics and having someone else solve it for you?
Sep
10
comment Equation for a line through a plane in homogeneous coordinates.
Also in 2D lines are dual to points, but in 3D lines are dual to lines, and planes are dual to points. In 2D a line can be viewed as a 3D plane normal to the paper, or a line lying on the paper. A 2D point is either a 3D line coming out of the paper or a 3D point lying on the paper. It depends on the context.
Sep
10
answered What is the d in the formula of a plane in $ R^3$
Sep
8
comment Equation for a line through a plane in homogeneous coordinates.
Note that a line between points $P_1=(\vec{p}_1;\delta_1)$ and $P_2=(\vec{p}_2;\delta_2)$ is defined by $$L=\begin{pmatrix} \delta_1 \vec{p}_2 - \delta_2 \vec{p}_1 \\ \vec{p}_1 \times \vec{p}_2 \end{pmatrix}$$
Sep
8
comment Give a unit vector perpendicular to vector $v=2i+3j$.
easy ... $k$. Oh you mean in 2D ?! Please edit the question to indicate so.
Sep
7
revised Equation for a line through a plane in homogeneous coordinates.
added 797 characters in body
Sep
7
answered Equation for a line through a plane in homogeneous coordinates.
Sep
3
comment Integrating with respect to time a double derivative $\ddot\phi + \frac bm\dot\phi = \frac{F}{mr}$
Is $F(t)$ or a constant?
Aug
31
answered Rotating Frame and Angular Velocity
Aug
29
comment Determine the general solution for $2\cos^2x-5\cos x+2=0$
Use \cos x instead of \rm{cos} x and use \mbox{..} for text within math (if needed).
Aug
27
comment How to find a vector normal to a cylinder in cylindric coordinates?
This question appears to be off-topic because it a simple search can yield the answer. See en.wikipedia.org/wiki/…
Aug
25
comment Second order Non-exact ODE by integral factor
See math.stackexchange.com/help/notation for math formatting hints.
Aug
25
answered Index notation for inverse matrices
Aug
21
answered conic sections, ellipse
Aug
21
answered Geometric meaning of line equation in homogeneous coordinate
Aug
21
answered Solving these two equations simultaneously