Use the Simplify > Approximate command, click on the icon on the command toolbar, or press Ctrl+G to approximate the currently highlighted expression or subexpression.  If only a subexpression is highlighted, the result is a copy of the whole expression with just the subexpression approximated.  


The Simplify > Approximate command and pressing Ctrl+G display a dialog box that allows you to enter the desired number of digits of precision used to approximate the expression and display the result.  For example, using 50 digits of precision

pi

approximates to 3.1415926535897932384626433832795028841971693993751.


When an expression is approximated by clicking on the icon, the number of digits indicated by the Precision fieldPrecision_field of the Simplification tab of the Options > Mode Settings command19_L5FP is used to approximate the expression, and the number of digits indicated by the Notation fieldControlling_Notation of the Output tab of the Options > Mode Settings command3L4YH is used to display the result.  For example, if the precision and notation are both 10 digits

pi

approximates to 3.141592653.


The APPROX function can be used on the expression entry line or in user-defined functions to approximate expressions.  APPROX(u,n) approximates expression u using n digits of precision.  n defaults to the number of digits indicated by the Precision fieldPrecision_field of the Simplification tab of the Options > Mode Settings command19_L5FP.


Simplifying expressions using the Simplify > Approximate command is the same as simplifying expressions using the Simplify > Basic command, except that the precision is temporarily set to approximate and the notation style is temporarily set to scientific.  


Most users prefer to run Derive in exact mode.  However, when necessary to approximate an expression, using the Simplify > Approximate command or the APPROX function avoids having to use the Simplification tab of the Options > Mode Settings command19_L5FP to switch back-and-forth between exact and approximate modes.


Other Simplify commandsSimplify_commands 

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