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For questions about inverses and pseudoinverses of matrices.

5 votes

Should the formula for the inverse of a 2x2 matrix be obvious?

Mnemonic: make the product diagonals the determinant, then scale. The off diagonals are zero because the area of a parallelogram with planar edge vectors $c_1,c_2$ is the length of the scaled project …
Tobias Hagge's user avatar