E-Code

How to define your own function on a TI-89 Titanium

By E-Code · updated

Press F4 (Other) and 1 for Define, type the name and rule like f(x)=x^2+1 (ALPHA | types f) and press ENTER for Done. Then f(3) ENTER gives 10.

Step by step

  1. Open the Other menu. F4 Press F4. On the home screen, F4 is the Other menu.
  2. Pick Define. 1 Press 1 for Define. It is pasted onto the entry line.
  3. Type f(x)=x^2+1. ALPHA | ( X ) = X ^ 2 + 1 Press ALPHA then | for f, then type (x)=x^2+1. The name goes left of =, the rule on the right.
  4. Save the function. ENTER Press ENTER. Done means f is saved, and it stays until you delete it.
  5. Type f(3). ALPHA | ( 3 ) Press ALPHA | for f, then (3). This asks for f when x is 3.
  6. Use it. ENTER Press ENTER. The TI-89 puts 3 in for x: 3² + 1.
  7. Read the answer. f(3) = 10. f now works like any built-in function: try f(a+1) for an answer in letters.

What the screen shows

f(3) = 10. f now works like any built-in function: try f(a+1) for an answer in letters.

Look for 10 on the screen.

Try it with the keys lit up

This guide is one of E-Code's Learn lessons. Open it on E-Code's TI-89 calculator and each key lights up in turn as you press it.

Try “Define your own function” on the TI-89 calculator

Related

Math programs for the TI-89 Titanium:

All TI-89 hidden tricks guides · All TI-89 guides · All calculator guides