DER2.81 (Second Derivative) freeware by Daniel Bishop (danb2k@hotmail.com) 2000-10-14 This program uses the centered difference formula to estimate the second derivative of a function (in this case, Y1), much like der2(y1,x,x) on the TI-86. To use this program, enter the function you wish to differentiate in Y1. Then, run the program and enter the value of X at which you want to evaluate the derivative. Prgm_:DER2 :.001 -> E :Disp "X=" :Input X :X+2E -> A :X-2E -> B :-2Y1 -> D :A -> X :D+Y1 -> D :B -> X :(D+Y1)/4E² -> D :Disp "DY1/DX=" :Disp D Sample Run: find f"(3) if f(x)=x³ "X^3" -> Y1 // before running the program, store f(X) in Y1 Done Prgm0 // substitute DER2's program number for the zero X= ?3 // user input DY1/DX= 18 // the derivative is 18, exactly the same as if done by hand