TI-36X Pro: Best bang for your 20 bucks

[Dave Britten]

Last week I needed a cheap calculator for doing regressions other than the basic four that the HP-48 is equipped with, so I grabbed a TI-36X Pro. Bottom line: despite being a barbaric algebraic monstrosity, you won't find a better calculator for the price.

Calling this the TI-36X Pro is rather misleading, because it's not even in the same league as the 36X, which was a functional, yet completely unremarkable scientific. The Pro has been upgraded with a dot-matrix LCD, and functionality that actually makes it a closer contender to the TI-83 and 86.

Most importantly, this is an "almost programmable" calculator. It doesn't give you any ability to write imperative programs, nor does it have functional programming like the 17BII solver. Instead, it has three neat features: set-op, list functions, and function definition.

Set-op is extremely simple to use. You press 2nd set-op, and at the prompt, type any expression or commands you want to evaluate, then press enter to save. Now on the home screen you can press 2nd op to execute that fragment either with whatever you've started typing already, or the value of Ans if the command line is empty. This is particularly useful if you need to do a bunch of conversions. Use set-op to enter ->Hex, ->DMS, a unit conversion, or whatever, then you need only enter an input and press 2nd op to repeat the calculation. If you use op repeatedly on the previous answer, a counter will increment showing the number of iterations (n=1, n=2, n=3...)

Function definition is similar, but allows you to define f(x)=expression. Then you can insert f(x) anywhere in a calculation to evaluate the function, or view a function table to explore multiple values.

The calculator gives you 3 lists for entering data, which can be used for statistical calculations. You can define any of these lists to be calculated based on values in the other two. If, for example, you're entering x values as time in H.MMSS format into L1 to save time during entry, and you want to convert these to decimal hours for calculations, you could define L3=iPart(L1)+iPart(fPart(L1)*100)/60+fPart(L1*100)*100/3600 and have L3 updated automatically. You would then use L3 for x values in any statistics, as the calculator allows you to select which list is x, which is y, and which (if any) contains frequencies).

The multi-tap keys are a cool idea to pack a lot of functions on the keyboard without a squadron of shift keys. For instance, there's a key labeled "sin sin^-1". Press it once to enter "sin". Press it again, and the function changes to "sin^1". Two further presses will get you "sinh" and "sinh^-1". Quite a few of the keys work this way, including trig, logs, powers, and probability.

Other features:

• Battery (CR2032) + solar dual power
• 8 storage variables (x, y, z, t, a, b, c, d)
• MathPrint mode, which displays properly formatted expressions as you type (think HP 48 Equation Writer), and is optional
• A few CAS-like features: fractions, square-root simplification, fractions of Pi
• Numeric integration and differentiation
• 1-or-2-variable stats
• Statistics distributions: normal, inverse normal, binomial, Poisson
• Regression: linear, quadratic, cubic, ln, power, exponential
• Matrix math (3 matrices, max dimension is 3)
• Vectors (3 vectors, max dimension is 3)
• Complex numbers
• Fraction conversion
• Base 2, 8, 16, Boolean logic operators
• Probability functions: factorial, nCr, nPr, random numbers
• Polynomial solver (quadratic and cubic)
• Numeric solver (separate equation, but you can use f(x), e.g. y=f(x))
• Linear system solver (2x2 or 3x3)
• Physical constants
• Unit conversions
  

Minor gripes:

The basic arithmetic operator keys are silver, and rather than having the symbols printed on the faces, they're molded slightly into the plastic. This is almost unreadable in any lighting conditions. Take an ultra-fine-point Sharpie and color them in, and it looks great. "Enter" would be hard to fill in because of the relatively light font, but you probably won't need to relabel that one.

Unit conversions are... functional. Definitely not too impressive, though, compared to all the other features. You've got 9 English/metric conversions (all two-way), conversions between F and C, or C and K (no Rankine?), 4 speed/length conversions (again, two-way), and pressure conversions between atm and Pa, or mmHg and Pa (no PSI?). I would have liked to see this more like the TI-86, where you have multiple categories of units, and can convert between them freely. Getting from gallons to cubic feet on the 36X Pro is quite a chore. (Convert gal to L, multiply by 1000 to get ccs, take the cube root, convert to inches, divide by 12 to get feet, then cube.)

Set-op being a shifted function is fine, but having "op" on a shifted key is disappointing. I think it would have made more sense to rearrange some of the functions on the keys just above the digits to get "op" a primary function, and make the fraction (x/y) function shifted. The 34 Multiview has TWO of them, op 1 and op 2, both unshifted, although it doesn't have to pack nearly as many functions onto the keyboard.

I love the list function feature, but if you try to define one and reference another list that doesn't have any data in it yet, you get an error. The same thing happens if you clear a list referenced by a list function: you get an error, and are forced to clear the formula. Keep a reference sheet handy if there are formulas you use frequently (like the decimal hours conversion) since they won't survive clearing of the referenced list.

Honestly, they should have called this something else, as the TI-36X Solar is a comparative weakling.