Specifically, https://math.mit.edu/~gs/linearalgebra/ila5/linearalgebra5_10-6.pdf https://math.mit.edu/~gs/linearalgebra/ila5/linearalgebra5_1... For more on

Specifically, https://math.mit.edu/~gs/linearalgebra/ila5/linearalgebra5_10-6.pdf https://math.mit.edu/~gs/linearalgebra/ila5/linearalgebra5_1... For more on the underlying geometry, see, e.g., https://archive.org/details/elementarymathem0000klei/page/70/mode/1up https://archive.org/details/elementarymathem0000klei/page/70... or, for a more modern, abstract formulation, https://archive.org/details/geometry0001berg https://archive.org/details/geometry0001berg