Linear Algebra
Transforming the plane…
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Linear Algebra
Transforming the plane…
Not a formula to memorise — the factor by which a matrix scales area in 2D and volume in 3D. Negative means flipped. Zero means squashed flat.
Start with the unit square: î and ĵ, area 1. Any matrix moves it to a parallelogram spanned by its two columns. The determinant is that parallelogram's area — with a sign.
ad − bc is the area of the parallelogram: the big rectangle (a + b)(c + d) minus the corner pieces that are not inside it.