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#### 6.8.5 Yacas Language Mode

The `d Y` (`calc-yacas-language`) command selects the conventions of Yacas, a free computer algebra system. While the operators and functions in Yacas are similar to those of Calc, the names of built-in functions in Yacas are capitalized. The Calc formula ‘`sin(2 x)`’, for example, is entered and displayed ‘`Sin(2 x)`’ in Yacas mode, and ‘‘`arcsin(x^2)`’ is ‘`ArcSin(x^2)`’ in Yacas mode. Complex numbers are written are written ‘`3 + 4 I`’. The standard special constants are written `Pi`, `E`, `I`, `GoldenRatio` and `Gamma`. `Infinity` represents both `inf` and `uinf`, and `Undefined` represents `nan`.

Certain operators on functions, such as `D` for differentiation and `Integrate` for integration, take a prefix form in Yacas. For example, the derivative of ‘`e^x sin(x)`’ can be computed with ‘`D(x) Exp(x)*Sin(x)`’ .

Other notable differences between Yacas and standard Calc expressions are that vectors and matrices use curly braces in Yacas, and subscripts use square brackets. If, for example, ‘`A`’ represents the list ‘`{a,2,c,4}`’, then ‘`A[3]`’ would equal ‘`c`’.