Casio fx-991ES
The fx- 991ES is a partially solar-powered calculator from Casio, whose special feature is the natural representation of mathematical expressions and formulas by a 31 x 96 dot matrix. He was released in 2005 as a successor to the fx- 991MS (which is a slightly lower range and only a single-line matrix display offers ).
- Fx- 991ES PLUS 2.1
- 2.2 fx- 991DE PLUS
Functions
The calculator provides a relatively high functional diversity, which is normally only available in graphical or programmable calculators. So it can calculate, among other definite integrals, create the table of values of a function or perform calculations with vectors. Moreover, it can solve systems of linear equations (within 3 equations with 3 unknowns ) in the rational number field, as well as cubic or quadratic equations in the complex number field. In addition, the common statistical functions can be calculated. The fx- 991ES allowed up to 24 levels of parenthesis, has saved 40 physical constants and 20 metric conversions dominated. He also has a so- Solve feature, with any equation can be solved by numerical approximation for the variable ( must not be used here, the integration, the summation and differentiation, as well as functions of combinatorics ).
Symbolic computation
The fx- 991ES generally translated numerically, gives results but partly as multiples of roots, fractures and constants:
- Rational numbers
- Square root expressions of the form with rational and natural
- Calculations and numerical identification of the circle with rational number.
That is numerically calculated and then recognized as a symbolic value.
- 15 °, 30 °, 45 °, 60 °, 75 °
Specifications
Criticism
The calculator got many test reports and reviews outstanding grades, especially in price-performance ratio. The missing key buffer and the resulting slow input speed but is often listed as a shortcoming. This problem was remedied in the subsequent models Casio fx- 991ES PLUS and Casio fx- 991DE PLUS. In addition, the partially slow execution speed (about when calculating certain integrals) criticized.
Successor models
Fx- 991ES PLUS
With the Casio FX- 991ES Plus Casio has the predecessor slightly revised the fx- 991ES. The calculator is since 2010 on the market and offers in comparison to its predecessor, a new design, a revised display, three additional variables memory and additional features such as a new equation mode or random integers. He has the same key arrangement so that a familiarization is not necessary if you change the fx- 991ES fx- 991ES Plus for.
Fx- 991DE PLUS
Since 2011, with the Casio fx- 991DE Plus an additional extension of the Casio fx- 991ES, which has been developed only for the German market. Its functionality has been expanded again in comparison to the fx- 991ES PLUS. Thus, with the FX- 991DE Plus distribution functions (normal distribution and inverse normal distribution, binomial distribution, Poisson distribution ) calculate and solve inequalities, which is not yet possible with the fx- 991ES PLUS. It can also determine the prime factorization of a maximum ten-digit natural number, but only prime factors are determined less than 1000. For example, the number 3647460817 as 7 ⋅ 11 ⋅ 13 ⋅ ( 3643817 ) is broken, the bracketing of the last factor indicates that it could contain prime factors greater than 1000.
When changing from Casio fx- 991ES fx- 991DE PLUS for a familiarization is different than the fx - 991ES PLUS but necessary because the keyboard size and user - menu have been adapted to German demands.
Admission to schools and colleges
Schools and colleges define which aids in concretely and calculators are allowed in the classroom and on exams. Frequently, for example, programmable calculators not allowed in exams. The Casio fx- 991ES / ES Plus is approved in most cases, in contrast to the model DE Plus, sometimes excluded because of advanced solution features linear equations. The Casio provides general admission guidelines. A prompt reply, only the respective school or college but can give.