Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In mathematics, Liouville''s formula is an equation that expresses the determinant of a square-matrix solution of a first-order system of homogeneous linear differential equations in terms of the sum of the diagonal coefficients of the system. The formula is named after the French mathematician Joseph Liouville. Liouville''s formula is a generalization of Abel''s identity and can be used to prove it. Since Liouville''s formula relates the different linearly independent solutions of the system of differential equations, it can help to find one solution from the other(s), see the example application below.