**Review: Texas Instruments TI-73 Explorer**
**Basic Information for the TI-73 Explorer**
Company: Texas Instruments

Production Years: 1998 - present(?)

New Cost: originally $95, went down to $70

Battery: 4 AAA with CR1616 backup

Memory: 25,000 bytes, 128K Flash ROM

Type: Graphing

There are three variants of the TI-73

Variant 1: 1998 - 2003. Gray keyboard, teal and blue keys.

Variant 2: 2003 - 2009. Renamed the TI-73 Explorer. Periwinkle keyboard, red, blue, and white keys. I have and am reviewing this variant.

Variant 3: 2009 - present. Same colors as Variant 2, but the calculator is shaped like the 2004 Monochrome TI-84 Plus.

All three variants have the same command set.

I purchased mine on eBay (thank you, molecularbonds) for $12.75. The best bet to buy one is to go online.

I think new units of the TI-73 Explorer are still being sold despite the fact that I have never seen it being sold in office and electronic stores or one "in the wild". If production has discontinued, it is a quiet discontinue.

**Background**
The TI-73 and the TI-73 Explorer was designed for the middle school market. The emphasis is on fractions, statistics, and basic algebra.

**Dedicated Fraction Keys**
There are five dedicated keys to fractions:

[UNIT]: Assists the user in entering a mixed fraction. Enter the whole number, press [UNIT], and a fraction bar comes up. For example, to enter 5 2/3, press 5 [UNIT] 2 [ ↓ ] 3 [ENTER].

[SIMP]: Simplifies fractions. This key only works in Mansimp mode. The key is non-function (a ERR:MODE error occurs in Autosimp mode).

[ b/c ]: Fraction bar. Assists the user in entering a fraction.

[F ←→ D]: Fraction/Decimal Conversion. On the TI-73, the maximum denominator is 1000. Any number 1/1001 or less will automatically be shown as its decimal equivalent.

[A b/c ←→ d/e]: Mixed Fraction/Improper Conversion. If you enter a decimal equivalent, the form you get depends on what mode the calculator is in.

A_b/c mode: The [A b/c ←→ d/e] converts the number in decimal form into an improper fraction.

b/c mode: The [A b/c ←→ d/e] converts the number in decimal form into a mixed fraction.

**Statistics**
The TI-73 performs one and two variable statistics. The available regressions are: Linear Regression (ax+b), Manual Fit (you set the line), Med-Med, Quad Regression (Quadratic Regression, ax^2 + bx + c), and Exp (Exponential Regression, a*b^x).

Like the TI-84 family (TI-80, TI-82 series, TI-83 series, TI-84 Plus series), the TI-73 has three stat plots. Unique to the TI-73, you can plot pie charts and horizontal and vertical bar charts with various symbols (such as people, trees, faces, pies, diamonds).

Further unique to the TI-73 (outside the CAS and Nspire series), lists on the TI-73 can hold strings. Each string can hold up to six characters. The lists with strings are used as category lists for pie charts and bar charts.

Speaking of strings, there is only one key with a variable, [ x ], but where did all the alpha characters go?

**The Text Facility: [ 2nd ] [MATH]**
Instead of an ALPHA key, the TI-73 has a text entry facility, which can be accessed by pressing [ 2nd ] [MATH]. The screen will allow you to write text strings. The quote character is included. You can use the keyboard to type numbers.

The text facility also has the comparison operators (=, ≠, >, ≥, <, ≤, with Boolean operators and, or).

When you are done, select DONE and press [ENTER]. Whatever is typed in copied to where your cursor was.

By the way, we can still use the variables A-Z to store values. This does make storing and recalling variables cumbersome.

**The Constant Key [CONST]**
The [CONST] key gives users four constant variables. Pressing [ 2nd ] [CONST] sets the constants. Unfortunately, we can not use the store key to store constants directly.

**Where Did All the Scientific Functions Go?**
Despite a keyboard that is simplified, the TI-73 has a range of mathematical functions. For example, the logarithmic functions are in the MATH-LOG menu. The trigonometric functions are in a separate menu. The hyperbolic functions have to be constructed.

[MATH]

MATH: lcm, gcd, cube, cube root, general root, solver

NUM: abs, round, iPart, fPart,min, min, remainder

PRB: rand, randInt, nPr, nCr, ! (factorial of integers), coin (toss a coin a number of times, results in a 0 or 1), dice (tosses any number of dice for a specific set of rolls)

LOG: log, 10^, ln, e^

[ 2nd ] [DRAW] (TRIG):

TRIG: sin, sin⁻¹, cos, cos⁻¹, tan, tan⁻¹

ANGLE: °, ', ", ^r (radian angle symbol), >DMS (conversion to degrees, minutes, seconds)

We may not have any calculus functions (integrals, derivatives, summation), but we have a good range of scientific functions.

**Graphing**
The only graphing mode available on the TI-73 is Functions (y(x)). Four graph slots are available.

**Programming**
The TI-73 has 25,000 bytes. All of the TI-BASIC commands are available, which includes If, For, While, Repeat, Input, Prompt, Output, IS>, and DS<.

The use of the TEXT facility is need to create strings, prompts, and labels. It will take getting used to since I'm used to an ALPHA key to work with.

**Conversions**
The [ 2nd ] [UNIT] (CONVERT) has many conversions of length, area, volume, time, temperature, mas, and speed. Always a good thing to have.

**Verdict**
I think the TI-73 could have been a great entry-level graphing calculator, like it a successor to the TI-81 or TI-80. I think the ALPHA key would help greatly.

I was not sure about the marketing strategy that the TI-73 didn't sell well. A lower price point would have helped too.

The TI-73 may be worth looking at getting, and if you do, I would try online sources like eBay to try to get it less than retail price.

With the 73, I now have all of the models of Texas Instruments graphing calculators (73, 80, 81, 82, 83, 84, 85, 86, 89, 92, Voyage 200, Nspire).

Source:

TI-73 and TI-73 Explorer. Datamath. Retrieved August 25, 2019

http://www.datamath.org/Graphing/TI-73.htm
http://www.datamath.org/Graphing/TI-73_Explorer.htm
http://www.datamath.org/Graphing/TI-73_Explorer_P1108.htm
Eddie

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