Yacas

Yacas provides symbolic manipulation through its own language, with scripts implementing many algebra operations and an online browser demo. The published tutorial keeps integer fractions exact, then uses N(expression, precision) when a numerical approximation is wanted; its precision argument is a digit count. Bodied derivative syntax places the expression after D(x) or D(x, order). The reference guide distinguishes working precision from a guarantee of accurate result digits: changing precision affects future floating-point work and does not recompute stored values. That matters when reusing an intermediate result created at lower precision. The software is LGPL 2.1-or-later, while its documentation has a separate licence.