Casio fx-991ES

The fx- 991ES

Casio fx-82MS, fx-991ES and fx-991EX compared

The fx-991ES is a solar and battery powered scientific calculator from Casio for schools and universities. Its special feature is the natural representation of mathematical expressions and formulas using a 31 × 96 dot matrix . It is not programmable. It appeared in 2005 as the successor to the fx-991MS.

Functions

The calculator offers a relatively wide range of functions that is otherwise only common with graphical or programmable pocket calculators. Among other things, he can calculate certain integrals , create a table of values for a function or perform calculations with vectors . In addition, he can solve linear systems of equations (max. Three equations with three unknowns) in the rational number range as well as cubic or quadratic equations in the complex number range. In addition, the common statistical functions can be calculated.

The fx-991ES allows up to 24 levels of brackets, has stored 40 physical constants and can do 20 metric conversions. Furthermore, it has a so-called Solve function, with which any equation can be numerically solved for the variable by approximation (integration, summation and differentiation, as well as functions of combinatorics, may not be used here). ${\ displaystyle X}$

Its predecessor, the "Casio fx-991MS", offers a somewhat lower range of functions and only a single-line matrix display.

Symbolic calculation

The fx-991ES always calculates numerically, but some results are given as multiples of roots, fractions and constants:

rational numbers in the form ${\ displaystyle {\ tfrac {a} {b}}}$
Square root expressions of the form with rational and natural ${\ displaystyle r {\ sqrt {n}} + s {\ sqrt {m}}}$ ${\ displaystyle r, s}$ ${\ displaystyle m, n}$
Calculation and numerical recognition of the circle number so that results are output as multiples of Pi in the form with rational . ${\ displaystyle r \ cdot \ pi}$ ${\ displaystyle r}$

This means that it is calculated numerically and then recognized as a symbolic value. ${\ displaystyle 4 \ arctan {\ tfrac {1} {5}} - \ arctan {\ tfrac {1} {239}} = {\ tfrac {\ pi} {4}}}$

${\ displaystyle \ sin x, \ cos x, \ tan x \}$ for 15 °, 30 °, 45 °, 60 °, 75 ° ${\ displaystyle x =}$

Technical specifications

Display	31 × 96 dot matrix (ES, ES PLUS, DE PLUS)
Number of characters / lines	Top line: 15 characters visible, bottom line: 12 + 2 characters visible - dot matrix display with "Natural Textbook" display. (ES, ES PLUS, DE PLUS)
accuracy	internal: 15 decimal places, 10 decimal places are displayed
Variable memory	6 variables (A, B, C, D, X, Y) and a balancing memory (M) (all fx-991 models)
Scientific constants	40
Metric conversions	20th
Number of functions	403 (DE PLUS: 580 , DE X: 696 )
Power supply	1 LR-44 backup battery Solar cell operation (preferred to save battery power) Automatic switch-off (adjustable between 10 and 30 minutes or completely off)
Dimensions	12.2 x 80 x 161 mm
Weight	104 g (including batteries and cover)

criticism

The calculator received excellent marks in many reviews and ratings, especially in terms of price-performance ratio. The missing key buffer and the resulting slow input speed is often listed as a shortcoming. However, this problem has been corrected in the successor models fx-991ES PLUS and fx-991DE PLUS. In addition, the sometimes slow execution speed (e.g. when calculating certain integrals) was criticized.

Successor models

PLUS models

On the Plus models, the middle navigation key is only oval in shape instead of circular. In addition, the blue color of the SHIFT, ALPHA, REPLY, MODE / SETUP and ON buttons is lighter. With the Plus models it is now also possible to enter numbers periodically, whereby the periodic view (display) of numbers was already possible with the fx-991ES.

fx-991ES PLUS

With the FX-991ES PLUS, Casio has slightly revised its predecessor, the fx-991ES. The calculator has been on the market since 2010 and, compared to its predecessor, offers a new design, a revised "Natural VPAM" display with the same resolution, three additional variable memories and additional functions such as a new equation mode or whole random numbers. It has the same key arrangement, so that you don't have to get used to it when you switch from the fx-991ES to the fx-991ES PLUS or fx-991DE PLUS.

fx-991DE PLUS

Successor model fx-991DE PLUS

Since 2011 there has been an additional expansion of the fx-991ES with the fx-991DE PLUS, which was only developed for the German market, so the menu language is mainly German. Compared to the fx-991ES PLUS, the functionality has been expanded to 580 functions. The FX-991DE PLUS can be used to calculate additional distribution functions ( binomial distribution , Poisson distribution ) and solve inequalities , which is not yet possible with the fx-991ES PLUS. The prime factorization of a maximum ten-digit natural number can also be determined, but only divisors smaller than 1000 are tested. For example, the number 3647460817 is broken down as 7⋅11⋅13⋅ (3643817), whereby the bracketing of the last factor should indicate that it could contain prime factors greater than 1000. Factors in brackets up to 1,000,000 are prime numbers, however, since a divisor greater than 1000 would always result in a divisor less than 1000.

Functions

function	Function description	FX991ES	FX991DE PLUS
COMP	Solving equations Prime factorization Fractions, periodic decimal fractions, e.g. B. ${\ displaystyle {\ frac {1} {47}} = 0, {\ overline {0212765957446808510638297872340425531914893617}}}$ LCM and GCD	✔ (1)	✔ (extended)
STAT		✔ (3)	✔
TABLE	Tabulate function values	✔ (7)	✔
DIST		×	✔
EQN		✔ (5)	✔
MATRIX		✔ (6)	✔
INEQ		×	✔
VECTOR		✔ (8)	✔
VERIF	Verify that calculations or equations are true. For example 142857 × 7 = (10⁶) -1 = 999999 (output: TRUE)	×	✔
CMPLX	Complex number calculation (represented at right angles or as polar)	✔ (2)	✔
BASE-N	Calculation with and conversion of decimal, hexadecimal, octal and binary numbers up to (2³¹-1) ₁₀ = (2147483647) ₁₀	(4)	✔

fx-991DE X CLASSWIZ

fx-991DE X

The fx-991DE X CLASSWIZ model, adapted to modern technical developments, has been available since March 2015. It has a high-resolution LC display with 192 × 63 pixels, four times the resolution of the previous models, and a processor that is around five times as fast. The functionality has been expanded to 696 functions. A significant improvement is the processing of 4 × 4 matrices with transformation in step form and the solving of systems of equations of the 4th order. This model also offers a spreadsheet, whereby the table contents are stored in the volatile memory and are therefore lost when switching off. Another new feature is that values and functions can be displayed as QR codes and analyzed online using a smartphone or displayed graphically.

Admission to schools and universities

Schools and examiners at universities determine which aids and, specifically, pocket calculators are allowed in lessons and exams. Often z. B. Programmable calculators are not allowed in exams.

The fx-991ES is approved in some cases, in contrast to the Plus models, which are sometimes excluded due to extended solution functions of linear equations. The FernUniversität in Hagen, for example, does not allow the “Casio fx-991” model series. Only the somewhat simpler models from Casio, the fx-86 and fx-87 (e.g. the current German model fx-87DE X CLASSWIZ ), are allowed for exams. The use of other than the permitted model series of pocket calculators "is assessed as an attempt at deception and sanctioned with the grade" insufficient "(5.0)".

Creation of teaching materials

All versions of the fx-991 model series are on the CASIO WEW Worldwide Education Website TrueType - Fonts available with the keyboard symbols for free. This allows the procedure for calculating z. B. explain clearly in word processing or presentation documents .

For LaTeX there is a package available with graph35 , with which key symbols and parts of the screen can be displayed . This is primarily intended for the Graph 35 and fx-9750GII pocket calculators , but can also be used for the fx-991 models with restrictions.

Individual evidence

↑ fx-991 ES user manual. Chapter Calculation Ranges, Number of Digits and Accuracy , p. G-80.
↑ Review of the FX-991ES (English)
↑ The largest prime factor that can be determined with the fx-991DE PLUS is actually 1,018,057 (the largest prime number less than 1009²), because 1009 is the smallest four-digit prime number and the first divisor that is no longer tested. From the successor model fx-991DE X, factors up to 1 018 057 are no longer bracketed.
↑ ^a ^b ^c fx-87DE X fx-991DE X Operating Instructions . CASIO COMPUTER CO., LTD .. Retrieved October 6, 2016.
↑ The links contained in the QR code refer to the Casio WES Worldwide Education Service .
↑ Helmut Gruber, Robert Neumann: CASIO fx-87DE PLUS / fx-87DE X from secondary school to high school: With detailed examples and exercises. . Freiburger Verlag, Freiburg im Breisgau 2015, ISBN 978-3-86814-319-5 (accessed on October 6, 2016).
↑ Study and examination information No. 3 summer semester 2016 . FernUniversität in Hagen, Hagen 22 June 2016, p. 24 (accessed on 6 October 2016).
↑ Procedure and rules of conduct for the exams . FernUniversität in Hagen. Archived from the original on October 6, 2016. Retrieved October 6, 2016.
↑ Briefs . In: CASIO WEW Worldwide Education website. Accessed on August 7, 2019 (fonts also available for other models such as CAS, graphics, standard and financial calculators from Casio).
↑ graph35 - Draw keys and screen items of several Casio calculators. In: Comprehensive TeX Archive Network . Retrieved August 7, 2019 .

Remarks

↑ In practice, the higher processor speed corresponds to a computing time that has been reduced to around a fifth. For example, the numerical calculation on the fx-991DE X CLASSWIZ takes 12 s instead of 58 s on the fx-991ES . ${\ textstyle \ int _ {10 ^ {- 10}} ^ {10 ^ {3}} {\ frac {1} {x}} \, \ mathrm {d} x}$

Web links

Commons : Casio fx-991 - collection of pictures, videos and audio files

Description of the fx-991DE PLUS on the manufacturer 's website
Test report about the fx-991ES at www.taschenrechner-test.de
Test report about the fx-991ES PLUS at www.taschenrechner-test.de
Learning videos for the fx-991DE PLUS at www.nachhilfetv.org
Detailed instructions for the fx-991ES at www.noxmiles.de

[1] x-991 ES user manual. Chapter Calculation Ranges, Number of Digits and Accuracy , p. G-80.

[2] Review of the FX-991ES (English)

[3] The largest prime factor that can be determined with the fx-991DE PLUS is actually 1,018,057 (the largest prime number less than 1009²), because 1009 is the smallest four-digit prime number and the first divisor that is no longer tested. From the successor model fx-991DE X, factors up to 1 018 057 are no longer bracketed.

[fx-87DEX_991DEX_Bedienungsanleitung-4] x-87DE X fx-991DE X Operating Instructions . CASIO COMPUTER CO., LTD .. Retrieved October 6, 2016.

[6] The links contained in the QR code refer to the Casio WES Worldwide Education Service .

[fx-87DE_X-7] Helmut Gruber, Robert Neumann: CASIO fx-87DE PLUS / fx-87DE X from secondary school to high school: With detailed examples and exercises. . Freiburger Verlag, Freiburg im Breisgau 2015, ISBN 978-3-86814-319-5 (accessed on October 6, 2016).

[FUH-4Taschenrechner-8] Study and examination information No. 3 summer semester 2016 . FernUniversität in Hagen, Hagen 22 June 2016, p. 24 (accessed on 6 October 2016).

[FUH-KlausurenTaschenrechner-9] Procedure and rules of conduct for the exams . FernUniversität in Hagen. Archived from the original on October 6, 2016. Retrieved October 6, 2016.

[10] Briefs . In: CASIO WEW Worldwide Education website. Accessed on August 7, 2019 (fonts also available for other models such as CAS, graphics, standard and financial calculators from Casio).

[11] graph35 - Draw keys and screen items of several Casio calculators. In: Comprehensive TeX Archive Network . Retrieved August 7, 2019 .

[5] In practice, the higher processor speed corresponds to a computing time that has been reduced to around a fifth. For example, the numerical calculation on the fx-991DE X CLASSWIZ takes 12 s instead of 58 s on the fx-991ES . ${\ textstyle \ int _ {10 ^ {- 10}} ^ {10 ^ {3}} {\ frac {1} {x}} \, \ mathrm {d} x}$