## Tip 71. Exclusion a number from symbolic conversions

### Fig. 71. Exclusion a number from symbolic conversions

The operator “:=” is used for setting numerical value of a variable in Mathcad (see tip 1). But sometimes it is necessary to make inverse operation – to deprive the variable of its numerical value as since it may prevent analytical transformations with help of the operator “→” – the reply will have number instead of symbol (see fig. 71):

There are three ways for solving this problem:

1.      Analytical transformations can be done in separate (subsidiary) Mathcad-document where all user’s variables do not have numerical values. Then you can transfer the results of the analytical transformations as separate mathematical insets, commentaries or pictures from the subsidiary Mathcad-document to the main one (see tip 63).

2.       In Mathcad there are tooling for deprivation a variable its numerical value. In Mathcad 6.0 PLUS the key word assume  was loaded with this function. In Mathcad 7/8/2000 Pro the “damping” of numerical value of a variable is done via the operator Vàã := Vàã that has no sense in the view of tradition programming languages (see fig. 71). The defect of this method is that the Mathcad-document is “soiled” by the operators that are not understandable for people who do not know all fine points of Mathcad. These operators can be concluded in an area (see tip 50) and then to close this area. But it can confuse even greater if somebody will try to display the document from a sheet.

3.      The variables that are used in numerical calculations and symbolic transformations may have the same names and can be written the same print (print, size and type), but at that they may relate to different groups of users (to different styles – see tip 52). This technology of parallel running numerical and analytical calculations is illustrated at the end of fig. 71: the variables of numerical calculations relate to a group (to style) Variables, but analytical ones – to a group User 7. At that for more clarity the name of the style User 7 can be changed to Symbolic, for example.