1. Introduktion
The Casio fx-85GTX is an advanced scientific calculator designed for students and professionals. It features a Natural-V.P.A.M. display, allowing mathematical expressions to be shown as they appear in textbooks. This model offers 276 functions, including advanced statistics, ratio calculations, and a variable list. It is dual-powered by solar energy and a backup battery, and comes with a protective slide-on hard case.

Image 1.1: The Casio fx-85GTX Scientific Calculator with its protective case.
2. Opsætning
2.1 Udpakning
Carefully remove the calculator from its packaging. Ensure all components, including the calculator and the slide-on hard case, are present. Retain the packaging for future storage or transport.
2.2 Strømkilde
The fx-85GTX operates using a dual power system: solar power and a single LR44 lithium metal battery. The calculator automatically switches between power sources depending on light conditions. The battery is pre-installed. Ensure sufficient light is available for solar operation, or that the battery has charge for low-light conditions.
2.3 Indledende tænding
Tryk på [PÅ] button to turn on the calculator. The display should show a clear screen. If the display is dim or blank, ensure adequate lighting for solar power or consider replacing the battery if the issue persists.
3. Betjening af lommeregneren
The Casio fx-85GTX features a clear 192 x 63 LCD display and a user-friendly menu system. Below are instructions for common operations.

Billede 3.1: Detaljeret view of the Casio fx-85GTX keyboard and Natural-V.P.A.M. display.
3.1 Grundlæggende beregninger
Indtast tal ved hjælp af det numeriske tastatur. Brug [+], [-], [×], og [÷] taster til aritmetiske operationer. Tryk på [=] for at vise resultatet.
3.2 Natural-V.P.A.M. Display
This feature allows input and display of fractions, roots, and other mathematical expressions in a natural format. For example, to enter a fraction, use the [ab/c] key. Square roots are entered using the [√] nøgle.
3.3 Menunavigation
Tryk på [MENU] key to access different calculation modes (e.g., Calculate, Statistics, Table, Ratio). Use the directional arrow keys to navigate and [=] or [AC] to select or exit.
3.4 Nøglefunktioner overview
- [FLYTTE]: Accesses secondary functions printed above keys in yellow.
- [ALFA]: Accesses tertiary functions printed above keys in red (variables, constants).
- [AF]: Sletter tegnet ved markørens position.
- [AC]: Clears all calculations and returns to the initial display.
- [ANS]: Recalls the last answer.
- [STO]: Stores a value to a variable.
- [RCL]: Recalls a value from a variable.
3.5 avancerede funktioner
The fx-85GTX includes 276 functions. Some notable functions are:
- Prime Factorization: Breaks down a number into its prime factors.
- Random Integer: Generates random integers within a specified range.
- Recurring Decimal Display: Shows decimal results as recurring decimals where applicable.
- Ratio Calculation: Solves ratio problems.
- Digit Separator: Improves readability of large numbers.
- Avanceret statistik: Performs various statistical calculations, including regression analysis.
- Advanced Tables: Generates numerical tables from functions.
- Variable List: Manages and uses multiple variables.
- Trigonometriske funktioner: Sinus, cosinus, tangent og deres inverse værdier.
- Logaritmiske og eksponentielle funktioner: Logarithms (base 10, natural) and exponential calculations.
4. Vedligeholdelse
4.1 Rengøring
To clean the calculator, wipe it with a soft, dry cloth. Do not use harsh chemicals, abrasive cleaners, or excessive moisture, as these can damage the display or internal components.
4.2 Udskiftning af batteri
The fx-85GTX uses one LR44 lithium metal battery. If the display becomes dim or erratic in low light conditions, the battery may need replacement. Refer to the battery compartment on the back of the calculator for instructions on how to open and replace the battery. Ensure proper polarity when inserting the new battery.
4.3 Opbevaring
When not in use, store the calculator in its protective slide-on hard case to prevent damage from drops, scratches, or dust. Avoid exposing the calculator to extreme temperatures, humidity, or direct sunlight for extended periods.

Image 4.1: The Casio fx-85GTX calculator with its protective slide-on hard case.
5. Fejlfinding
5.1 Displayproblemer
- Mørkt eller blankt display: Check lighting conditions for solar power. If in low light, the battery may be depleted. Replace the LR44 battery if necessary.
- Forvrænget skærm: Prøv at trykke på [AC] button to clear. If the issue persists, perform a full reset (see 5.2).
5.2 Nulstilling af lommeregneren
If the calculator malfunctions or displays incorrect results, a reset may resolve the issue. To perform a full reset, press [FLYTTE] så [9] (RESET). Select the desired reset option (e.g., 'Setup Init' or 'All'). Confirm the reset by pressing [=]. Note that resetting will clear all memory and settings.
5.3 Incorrect Calculation Results
Verify that the calculator is in the correct mode for your calculation (e.g., DEG for degrees, RAD for radians). Check your input values and the order of operations. If the issue persists, try resetting the calculator.
6. Specifikationer

Image 6.1: Casio fx-85GTX dimensions: 16.6 cm (length) x 7.7 cm (width).
| Feature | Specifikation |
|---|---|
| Modelnummer | fx-85GTX |
| Antal funktioner | 276 |
| Display Type | LCD (192 x 63 pixels), Natural-V.P.A.M. |
| Strømkilde | Solar powered with 1 x LR44 Lithium Metal Battery |
| Dimensioner (L x B) | 16.6 cm x 7.7 cm |
| Materiale | Plast |
| Farve | Sort |
| Vægt | Approximately 90 g (without cover) |
| Oprindelsesland | Frankrig |
7. Garantioplysninger
For specific warranty details, please refer to the warranty card included with your product at the time of purchase or consult the retailer where the calculator was acquired. Casio's warranty terms typically cover manufacturing defects for a specified period from the date of purchase.
8. Support
If you encounter issues not covered in this manual or require further assistance, please contact Casio customer support. Contact information can typically be found on the official Casio website for your region or through the retailer from whom you purchased the product.