The TI-84 is a graphing calculator that is made by TI, or Texas Instruments. The TI-84 comes in two versions, the Plus and the Plus Silver. Released in 2004, it is faster and has a higher contrast screen than the TI-83 Plus. The "θ" is a lower-case Greek letter. In mathematics, the theta -- or "θ" -- is frequently used as a variable to represent an angle. It is used in trigonometry and with polar coordinates.

Enter any characters in the expression that will be before the "θ."

Press the “ALPHA” key.

Press the “3” key. The "θ" will now be displayed.

Enter any remaining characters to complete the expression.