The Evaluate option in the Tools menu allows you to quickly find the value of any equation you've entered at a specific point. Before choosing the Evaluate command, you may select an equation to work with by highlighting it in the redraw queue. Differential equation slope fields cannot be evaluated at a point since they are not explicit functions of one variable.

If you've selected a valid equation, the Point Evaluate dialog box will appear, and the equation you are working with will be displayed on the status line. You can now type in points at which you want to find the value of the function at leisure. For angle measurements, your input values are assumed to be in radians; multiply by the constant `d`

to convert from degrees. You can also use the constant `pi`

to make entering precise radian numbers easier. In fact, any expression you could type in as part of an equation that evaluates to a constant is valid.

When you press enter or click the Calculate button, Graphmatica will calculate the value of the dependent variable(s) at this point and display the result. For families of functions using the parameter `a`

, only the starting value of `a`

will be used, since only one result is displayed. (Note: if an error occurs when evaluating at the point, a message will be displayed on the status line regardless of the state of the Warning Messages option.) Continue typing in numbers and observing the results as long as you wish, then press ESC or click the Close button to dismiss the dialog box.

For Cartesian functions, you can also enter a value for the dependent variable and solve for the independent variable. (This is found using Newton's method; hence it is not available for relations that are not functions.) In this case you may enter a value to use as a guess for the independent variable, and the program will find the solution closest to that guess.

For implicit functions, Graphmatica calculates and displays up to 5 y values for a given value of x.

If you want to see the values of points on multiple equtions at once, turn the Point Tables option on. Each result that is printed in the dialog box will also be added to the Point Tables window.

kSoft, Inc. ksoft@graphmatica.com Last updated: Sun 11 Jun 2017