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Tool for calculating a change of basis matrix based on a homothety or rotation in a vector space and coordinate change calculations.

Answers to Questions

How to calculate change of basis equations?

From a transformation matrix $ P $ (also called base change of basis matrix), any vector $ v $ then becomes the vector $ v' $ in the new base by the computation (dot / multiplication">matrix product) $$ v' = P.v $$

From a rotation angle $ \alpha $ (trigonometric direction) and an axis, the rotation matrix is written as (rotation around the axis $ z $) $$ \begin {pmatrix} \cos \alpha & - \sin \alpha & 0 \\ \sin \alpha \cos \alpha & 0 \\ 0 & 0 & 1 \ \end{pmatrix} $$

From 2 vectors (the original and the destination one), it is possible to generate an equation system to solve to find the values of $ \alpha $ and the axis.

How to calculate an homothety matrix?

From the value of the scaling factor $ k $ (homothety assumed to be uniform throughout the vector space of size $ n $), the passing matrix is given by the formula $ k.I_n $ (with $ I_n $ the identity matrix).

Source code

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