Special attention will be attached to the problem of solving the equations since the explosion of terms in the solutions is the main problem in symbolic circuit analysis. Three fundamental approaches for the automated approximation of circuit transfer function and circuit equations will be presented which allow for the extraction of dominant circuit behaviour - linear and even nonlinear. These approximation strategies are based on combining symbolic and numeric information: They hold the key for gaining insight in how circuits work, and the obtained results may even be used for the generation of sizing formulas. From a mathematical point of view these new mixed symbolic-numerical approximation strategies open up a large field of unsolved problems.
