The Casio fx-991ES Plus is a popular scientific calculator widely used by students and professionals for its range of functions and user-friendly interface. Here are its key features:

🔹 General Features:

Natural Textbook Display: Shows mathematical expressions (fractions, roots, integrals, etc.) as they appear in textbooks.

High-resolution LCD display for better readability.

Solar + Battery Powered (dual power system).

Multi-replay function to recall previous entries and modify them.

🔹 Calculation Features:

✅ 417 Functions including:

Basic arithmetic

Fractions and decimals

Roots, powers, and reciprocals

Logarithms and exponentials

Trigonometric & Inverse Trig Functions

Hyperbolic Functions

🔹 Advanced Math Functions:

✅ Matrix and Vector Calculations

✅ Complex Numbers

✅ Equation Solving (linear and quadratic equations)

✅ Inequality Solving

✅ Integration and Differentiation

✅ Statistical Calculations (standard deviation, regression analysis)

✅ Base-n calculations (binary, octal, decimal, hexadecimal)

🔹 Convenient Tools:

✅ Scientific constants (like Pi, e, etc.)

✅ Conversion functions (e.g., angle units: degrees ↔ radians ↔ grads)

✅ Table function for generating tables of values

✅ Random number generator

🔹 Design & Usability:

Lightweight and compact

Durable plastic keys

Hard cover for protection