Casio FX-115ES Calculator

The Casio FX-115ES is sold in Asia as the Casio FX-991ES. It's the same calculator, except for the model number. The power supply is a solar panel supplemented by a single LR44 battery.

In evaluating calculators of this type, I tested the Casio FX-115ES alongside the Casio FX-65, the Sharp EL-506WBBK, the Sharp EL-W535B, and the TI-80X. Although the Sharps were about as featured as the FX-115ES, the FX-115ES outperformed them in tests of computational accuracy such as evaluating the tangent of 355/226, the sine of 1E8, and the 3/5 power of -32.

All the usual scientific calculator functions are present, plus a few that you don't often see, such as log to any base, absolute magnitude, mixed and improper fractions with conversion to decimal, Riemann sums, numerical integration and differentiation. The Casio FX-115ES uses Gauss-Kronrod quadrature for integrals, instead of the usual Simpson's rule, which seems to give better results for some integrands.

The log-to-any-base feature includes the possibility of making the base of the logarithm, itself, a function of the independent variable.

The Casio FX-115ES will hold equations for multiple calculations of Y for different values of X, so that points (X,Y) can be generated quickly by repeatedly pressing the CALC button and entering X when prompted. The equals sign (=) used with functions is in the upper left corner of the calculator panel as ALPHA CALC.

It will also SOLVE functions in reverse. For example, given the function Y=X-Asin(X) with the calculator in radian angle mode, pressing 2nd SOLVE will prompt you to input Y and A, after which the calculator would solve for X. If Y=4 and A=0.8, then X=3.626850697. Note that solving a transcendental function for the value of the transcendental variable is not a problem for the Casio FX-115ES.

The CALC and SOLVE features give calculators having them a tremendous advantage in ease of use over calculators that don't have them. Entered functions, integrals, and derivatives can be edited by using the directional button (the big circular one) and the DEL key.

The Casio FX-115ES provides 40 physical constants as well as 40 units conversions. It will also convert from decimal degrees (or decimal hours) to DD.MMSS format and the reverse.

The statistics mode offers seven two-variable regression models (linear, quadratic, logarithmic, e exponential, ab exponential, power, and inverse), plus the usual single variable statistics function is also available.

The vector & complex calculations can be swapped between rectangular and polar coordinates. The available alternate bases, besides decimal, are hexidecimal, binary, and octal. The math capabilities of the fx-115ES are truncated in any of the bases other than decimal.

The Casio FX-115ES isn't perfect. It's just the best there is at present. Room for improvement certainly exists. First, there is no good reason why a calculator can't use any base > 1 directly with any of its functions. Nor is there any reason why alternate base results can't be displayed in fractional or post-dot digital form.

Second, the matrix operations are restricted to a maximum size of 3x3 matrices. Students who apply the theory of relativity need at least 4x4 matrix operations. And bigger, of course, would be better.

Third. The factorial key should be supplemented by a gamma function.

If you need more calculator than the Casio FX-115ES, you probably should buy a TI-89 Titanium. More than that requires a desktop computer.

IMO Casio scientific calculators are much better than the TI ones.
Casio fx-115 is much easier to operate and shows your calculations in a textbook style. i bought a $ 15 Ti and a $ 15 casio and the difference between the two is remarkable.
for one the TI only has one mode which is standard mode while the casio has 8 different modes ranging from equations to statistics and vectors.
the TI performs basic calculations while the casio can integrate and deal with complex numbers.
all in all the casio is a very well built calculator and i have used it all through high school and am still using it in college. Recommended

Love this calculator. Originally purchased a TI-30XS Multi View which is a nice calc. also, but the Casio is far and away a better unit for the cost and the features it has. The Casio for instance has a small battery compartment in the back which facilitates easy removal/replacement of the single LR44 cell. The TI unit needs to be disassembled with a tiny phillips screwdriver and the entire back must be removed. Granted, the batteries last many, many moons, but still it should have been designed more user-convenient. Also the display on the Casio if far superior to that of the competition, very readable with no eye strain at all.

Just get one of the 115ES's and you won't be disappointed, I promise you.

I bought the Casio fx-115ES last weeks and was immediately impressed with the number of features available on this inexpensive calculator. It has a two line natural display features, that makes it rock!. The calculator its a little light weight compared to may recent calculator that i used back on my college days. I no have complains or any issue regarding the product, even though its a used one. There's no scratch on it, and looks like new. I recommend you must have one of this.

The calculator exactly I wanted for my mathematical calculations. It has all the basic and scientific functions required. Good for any engineering student.