Fx 991ES Plus Calculator Online

User Guide: Casio fx 991ES Plus Calculator

1. Calculator Overview

The calculator mimics the real Casio fx-991ES Plus, featuring:
✅ Basic Arithmetic (+, -, ×, ÷)
✅ Scientific Functions (sin, cos, tan, sin⁻¹, cos⁻¹, tan⁻¹, √, ^)
✅ Memory & Display (STO, RCL, ANS, DEL)
✅ Dual Display (Main & sub-display for operations)

2. Basic Operations

Entering Numbers

• Click the number buttons (0-9) to input digits.
• Use the decimal point (.) for floating-point numbers.

Arithmetic Calculations

1. Enter the first number (e.g., 5).
2. Press an operation button (+, -, ×, ÷).
3. Enter the second number (e.g., 3).
4. Press = to see the result.

Example:

5 × 3 = 15  

3. Scientific Functions

Trigonometric Functions (sin, cos, tan, sin⁻¹, cos⁻¹, tan⁻¹)

1. Enter a number.
2. Click the desired function (e.g., sin).
3. The result will display.

Example:

sin(30) → (Result depends on angle mode)  

Exponents & Roots

• Square Root (√): Click after entering a number.
• Power (^): Enter base, click ^, enter exponent, then =.

Example:

2 ^ 3 = 8  
√16 = 4  

4. Memory Functions

Example:

5 + 3 = 8  
Press STO → Value stored  
Press RCL → 8 reappears  

5. Clearing & Resetting