sympy/sympy — pull request #2185 by cheatiiit (2013-06-17 23:08:48+00:00)
Title: Algorithms for solving Coupled Differential System.

This method is used for solving Coupled Differntial System.
Given a differntial field K of characterstic 0 and f1, f2, g1, g2
in K, it decides whether the system of equations
/ \ / \ / \ / \
| Dy1 | | f1 af2 | | y1 | | g1 |
| | + | | | | = | |
| Dy2 | | f2 f1 | | y2 | | g2 |
\ / \ / \ / \ /

Hence returning (y1, y2) if a solution exist, None otherwise