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New section §11: A × adj(A) = det(A) × I Cofactor identity infrastructure: - cofactorSign: checkerboard (-1)^(i+j) - cofactorProductEntry: Σ_k A[i][k] × adj(A)[k][j] - Verified by #eval on identity, diag(2,1,...,1), permutation, zero-row, equal-rows Proved theorems (by native_decide on concrete matrices): - cofactor_identity_identity_diag: I × adj(I)[i,i] = det(I) - cofactor_identity_identity_offdiag: I × adj(I)[i,j] = 0 for i≠j - cofactor_identity_diag2: diag(2,1,...) × adj = det × I - det_self_inverse_exact_diag2: diag(2,1,...) × inv = I Optimization shortcuts (from user guidance): - bestRow/bestCol: choose expansion line with most zeros - hasZeroDeterminant: zero row / equal rows → det = 0 - isUpperTriangular/isLowerTriangular: det = product of diagonal - triangularDet: product of diagonal for triangular matrices General cofactor_identity: sorry (needs equal-rows→det=0 lemma) det_self_inverse_exact_from_cofactor: sorry (proof sketch complete) det_self_inverse: sorry (Q16_16 obstruction, documented) lake build: 3300 jobs, 0 errors |
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| conversions/hardware | ||
| external/OTOM | ||
| LeanGPT | ||
| Semantics | ||
| CHAIN_ALL_REVIEW_REPORT.md | ||