Statement of Liouville's Formula
Consider the n-dimensional first-order homogeneous linear differential equation
on an interval I of the real line, where A(x) for x ∈ I denotes a square matrix of dimension n with real or complex entries. Let Φ denote a matrix-valued solution on I, meaning that each Φ(x) is a square matrix of dimension n with real or complex entries and the derivative satisfies
Let
denote the trace of A(ξ) = (ai, j (ξ))i, j ∈ {1,...,n}, the sum of its diagonal entries. If the trace of A is a continuous function, then the determinant of Φ satisfies
for all x and x0 in I.
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