# SLOPEFIE for the Texas Instruments TI 85:

SLOPEFIE sketches a field of sample slopes for solutions of , where g is any reasonably well-behaved function.

To enter the program, select 'PRGM', 'NEW'. When 'Name =' appears, type in 'SLOPEFIE',then press the 'ENTER' key. When you have finished typing in the program, press '2^{nd}QUIT'. To run the program, select 'PGRM', 'NAMES', 'SLOPEFIE'.

PLEASE NOTE: '>' and '<' can be entered from the 'TEST' menu; '' can be entered by pressingthe 'STO>' key; and all other function names, text, label and variable names are typedin from 'ALPHA' mode. Everything else is entered as a single keystroke on the calculator(for example, '+' is entered by pressing the '+' key).

## Program:

SLOPEFIE uses the plot parameters set in the WINDOW function (xScl and yScl are used asthe sample grid size).' The value of must be typed (in the equation mode ), as . For example, in the given program, , so .

**NOTICE:** In writing this equation, you *must* use lower casenames for both variables, *x *and *y.*

Check: The slope field for , for

xMin = -3, xMax =3, xScl = 0.3, yMin = -2, yMax =2, yScl = 0.3

is sketched on the right.

**Please Note:** There are at least two significantly different versions of the TI 85.One of these versions appears to have a software bug that distorts the slopefield plot inthe left-most column of vectors. Since this problem is caused by an error in thecalculator's system software, we have no 'work-around'. Students who choose to use thisversion of the TI 85 will have to be careful to take this defect into account.

(jac) Lastrevised: December 03, 1998