Welcome to blog entry #73. Just an announcement:

Starting Monday on April 23, 2012, I begin my Calculus Revisited Series, where we revisit some of the major topics of calculus. Each blog entry is going to contain a quick summary of the topic, followed by a few example problems. Hopefully this serves as a review for students in calculus in time for finals or perhaps you want to revisit some of the topics. It will be one blog each day, Monday through Thursday except on Friday, where you get three for the price of one. (don't worry, it's free).

Onto today's topic... the Casio fx-115ES Plus Calculator Review!

The fx-115ES PLUS is the successor to the 2006(?) [when was this calculator first released?] fx-115 ES. Outside of the United States, these calculators are called fx-991ES PLUS and fx-991 ES, respectively.

I purchased the fx-115ES PLUS at a WalMart in Glendora, CA. Apparently, this is the only major store at this time that carries the new fx-115ES PLUS outside of ordering online. It cost me $17.48, around the same price the classic fx-115 ES cost.

The picture below is a comparison between both models. The new fx-115 is on the left.

**Features**

The fx-115ES PLUS retains the Natural-V.P.A.M. (Visually Perfect Algebraic Method), which means that you can enter equations and expressions exactly as written. The MathIO method allows the user to accomplish just that. Fractions, radicals, expressions with π, and calculus function templates are all there. Exact answers can include fractions, square roots, and coefficients of π (MathIO).

For those who want a older style, one-line entry method, the LineIO method has been retained. Personally, I prefer the MathIO method.

All of the other features that were present in the classic fx-115 ES are here to:

* Integrals of f(x)

* Numeric Derivatives: d/dx

* Sums of a function: ∑ f(x)

* Base modes Decimal, Octal, Binary, Hexadecimal

* Numeric solver, of equations and roots of expressions. Yes, the variable to solve for is X. (see below)

* CALC button allows for calculating expressions repeated amount of times.

* Statistics including 1-variable, linear regression (a+bx), quadratic regression (a+bx+cx^2), cubic regression (a+bx+cx^2+dx^3), 2 types of exponential (a + b * e^x and a x^b), power (b a^x), logarithmic (a + b ln x), and inverse (a + b/x).

* Equations - 2x2 and 3x3 simultaneous equations, quadratic, and cubic equation

* Matrices: functions include transpose, inverse, and determinant

* Vectors

* Multi Line Statements with the colon (:)

* Complex Number Mode - unfortunately it's still limited to arithmetic, x^2, 1/x.

Hint: To clear calculator history, while in COMP mode, press the [ ON ] key.

Hint: To force approximate answers, press [SHIFT] [ = ]. This works on both versions of the fx-115 ES. **What's New?**

* The number of available memories have increased from 7 to 9. (A, B, C, D, X, Y, M, and now E, F). Previously E and F were available only for the Hexadecimal mode.

* You now have the ability to calculate using repeated numbers. For example, you can type the decimal form of 1/3 using 0.3 with the bar above the three. I believe that this is first line of calculators that has this ability.

* New number functions are: GCD, LCM, Integer Part, Fractional Part, Random Integers, Integer Division (÷R) that gives quotient and remainder, and Prime Factorization (up to three digit factors). To factor a number, enter it, press [ = ], then [SHIFT], [ º ' '' ].

* Products of function f(x): ∏ f(x).

* In Table Mode you can include two functions f(x) and g(x). This is turned on in SET UP.

* The [ALPHA] key acts as both as an variable key and a second shift key.

* The rref and ref functions are added to the Matrix Mode (but not eigenvalues).

* The fx-115ES PLUS has a curve design, and boasts a faster processor. **New Modes**

* Inequality Solver of quadratic and cubic equations

* Verification mode, used for compare expressions (i.e. Does π/4 < π/2? Does 1 = 9/9 = e^0?)

* Distribution mode: Normal Distribution (CDF, PDF, and Inverse (Yes!)), Binomial Distribution (CDF, PDF), and Poisson Distribution (CDF, PDF).**Final Thoughts**

If the fx-115 ES was solid, then the fx-115ES PLUS is taking a great calculator and making it better. At about $18, you get a huge bang for the buck.

Rating: ***** (5 out of 5)

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UPDATE-CORRECTION**Many thanks to jcroot** for pointing this out to me:

The Solve feature can solve for more than just X. You can specify the variable as so:

equation, variable to solve for

If there is no second argument, then the variable to solve for defaults to X.

Example:

X - 2Y = 1, X solves for X

X - 2Y = 1, Y solves for Y

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This blog is property of Edward Shore. © 2012