Texas Instruments TI-92 Owners Manual - Page 354

Defining the Known Variables After you type an equation in the Numeric Solver, enter the applicable values for all variables except the unknown variable. Defining the List of Variables Note: If an existing variable is locked or archived, you cannot edit its value. After typing your equation on the eqn: line, press ¸ or D. The screen lists the variables in the order they appear in the equation. If a variable is already defined, its value is shown. You can edit these variable values. The solution must be within the specified bounds, which you can edit. Enter a number or expression for all variables except the one you want to solve for. Notes and Common Errors Note: When you assign a value to a variable in the Numeric Solver, that variable is defined globally. It still exists after you leave the solver. ¦ If you define a variable: − In terms of another variable in the equation, that variable must be defined first. − In terms of another variable that is not in the equation, that variable must already have a value; it cannot be undefined. Since a is defined in terms of g, you must define g before a. When you move the cursor to another line, g/3 is evaluated. − As an expression, it is evaluated when you move the cursor off the line. The expression must evaluate to a real number. ¦ If the equation contains a variable already defined in terms of other variables, those other variables are listed. If variable a was defined previously as b+c!a, then b and c are listed instead of a. ¦ If you refer to a previously defined function, any variables used as arguments in the function call are listed, not the variables used to define the function. If f(a,b) was defined previously as ‡(a^2+b^2) and your equation contains f(x,y), then x and y are listed, not a and b. Chapter 19: Numeric Solver 337