The Casio 991ES Plus is a scientific calculator designed for students and professionals. It is widely used in educational settings for its functionality, ease of use, and affordability. Here are its key features:
1. Natural Textbook Display: This feature allows the display of mathematical expressions (fractions, square roots, integrals, etc.) just as they appear in textbooks, making it easier to read and understand calculations.
2. Multi-replay Function: You can recall and edit previous calculations, which is useful for revising steps or correcting mistakes without starting from scratch.
3. Functions and Operations: It supports over 400 functions, including:
Basic arithmetic and algebraic operations
Trigonometric, logarithmic, and exponential functions
Statistical functions like mean, standard deviation, and regression
Complex number calculations
Equation solving and matrix/vector calculations
Integration and differentiation
Base-n calculations (binary, octal, hexadecimal)
4. Power Source: Dual power system (solar and battery-powered) ensures reliable performance and extended usage life.
5. Durability and Portability: Compact, lightweight, and durable, the 991ES Plus is easy to carry and can withstand daily use in school or professional settings.
Overall, the Casio 991ES Plus is known for its reliability and versatility, making it a popular choice for complex mathematical, statistical, and engineering calculations.
