General: To enter the program into the calculator, press the programming key (middle upper key), then C (which selects the NEW program option), then ENTER, then 1 (to select REAL mode), then the program name. The calculator will be in A-LOCK mode. Hit ALPHA at the end of the name, and then ENTER. After typing each command, press the ENTER key.
Commands: Explanation and keying instructions ClrG Clears the screen. COMMAND (2ndF MATH),E,1 Goto start This program begins with a subroutine fn which gives the function of x and y defining the slope. For Goto and Label press COMMAND, then B for BRNCH menu; Label fn then 2 for Goto, 1 for Label. f=-x/y ONLY LINE to be changed for a new function -x/y is only an example!! Note: f here is a function of both x and y. Return For Return, get to BRNCH mode as above, then press 5 key. Label start "start" is here. h=7(-xmin+xmax)/83 Program will prompt for the unspecified variables xmin,xmax,ymin,ymax. Remember to use the (-) sign next to ENTER. k=7(-ymin+ymax)/55 For /, press the division key, under the the ) key. These instructions calculate the x and y increments. Range xmin,xmax,1,ymin,ymax,1 For Range, press COMMAND, then D for GRAPH menu, then 4. This instruction will be used when drawing the field. a=1/(0.4h)^2 Instead of ^2 one can press the key b=1/(0.4k)^2 left of the log key. The numbers a and b are used in calculating how long the line segments will be. x=xmin+0.5h These instructions locate the initial lower z=ymin+0.5k left-hand point. i=1 Initializes the column count. Label 1 j=1 Initializes the row count for each new column. y=z Label 2 Gosub fn c=1/sqrt(a+b*f^2) HERE, DO NOT ENTER THE LETTERS sqrt, BUT INSTEAD PRESS THE KEY to the left of the STO key! Calculator will show a radical. s=f*c * is the multiplication key, under the ( key. The numbers c and s will give the horizontal and vertical components of the line. u=x v=y Line u-c,v-s,u+c,v+s For Line press COMMAND,D,7 key. Note: comma is on the . key, in ALPHA mode. Draws a line centered at the current (x.y) y=v+k Move up in the column. j=j+1 If j< =8 Goto 2 For If and Goto go to BRNCH mode as before, then press 3 key for If and 2 key for Goto. For < = press COMMAND, then C for INEQ menu, then 3. Are we still in this column? If so go back to "2". x=u+h Otherwise move over to next column. i=i+1 If i< =12 Goto 1 Check if all columns are done. DispG Display graph: COMMAND (2ndF MATH),E,4Running the program: Remember to re-edit when you switch functions, and that dy/dx = f(x,y) is a function of two variables. Then get to the program menu (upper middle key), choose A (for RUN menu), then right arrow, then down arrow to SLOPE, then ENTER. After graph is drawn, press ON key, then CL key.
Check: For f = -x/y get circles centered at the origin. The circles
will be round if your screen
parameters have the correct aspect ratio.
Check: For f = x+y and window [-3,3]x[-2,2], calculator screen should have the image shown on the right.