Using a Calculator

Main Content

Using a Calculator Efficiently

Getting to know your calculator

A scientific calculator is an essential tool for mathematics. To use it efficiently, you need to understand its features and practice using them correctly.

Different calculator models look slightly different, but they all have the same basic functions. The most common type used in schools is the Casio fx-83GT or similar models. Even if you have a different brand, the principles are the same.

Important initial settings

Before you start any calculation, check your calculator is set up correctly:

• Mode setting: Your calculator should be in 'MATH' mode (sometimes called normal mode). Look at the top of the display screen – you should see the word MATH or a symbol indicating this mode.

• Angle unit: For most IGCSE questions, angles must be measured in degrees (not radians). Check your calculator display has a 'D' symbol at the top. If it doesn't, press the SETUP button and change the angle unit to degrees.

• Answer format: You should know how to switch between exact answers (like fractions) and decimal answers. Most calculators have an S⇔D button that switches between these formats.

Essential calculator buttons

To work efficiently, you need to know where these important buttons are:

• Fraction button (usually marked as a÷b or similar): Lets you enter fractions directly
• Square button (x²): Squares a number
• Cube button (x³): Cubes a number
• Power button (x^□): Raises a number to any power
• Square root button (√): Finds the square root
• SHIFT button (sometimes called 2nd or INV): This unlocks extra functions. For example, SHIFT + √ gives you cube root (∛)
• Brackets buttons ( ): Very important for entering calculations correctly
• Negative button (−): This is different from the minus button. Use this for negative numbers
• Standard form button (×10^x): For entering very large or very small numbers
• π button: Gives you the value of pi (usually accessed with SHIFT)
• Trigonometry buttons (sin, cos, tan): For triangle calculations
• Inverse trigonometry (sin⁻¹, cos⁻¹, tan⁻¹): Accessed using SHIFT, used for finding angles
• ANS button: Recalls the last answer your calculator worked out

Why brackets are crucial

Brackets help your calculator understand the order of operations correctly. Always use brackets when:

• You're dividing by an expression (e.g., to calculate 8 ÷ (2 + 3), you must put brackets around 2 + 3)
• You're entering negative numbers into calculations
• You're working with powers of negative numbers

Important note: −3² is NOT the same as (−3)²

• −3² means "the negative of 3 squared" = −9
• (−3)² means "negative 3, all squared" = 9

Always use the (−) button for negative values, not the subtraction button.

Working with trigonometry

When you press sin, cos, or tan, the calculator automatically gives you an opening bracket. Remember to close it with a closing bracket after you enter the angle.

For example: sin(45) not sin(45

To find an angle (inverse trigonometry), use SHIFT then the trig button. For example, SHIFT sin gives you sin⁻¹.

The ANS function

The ANS button is very useful when you have a multi-step calculation. It stores the last answer the calculator calculated. This means you don't have to write down or re-enter long decimal numbers between steps.

For example:

• Step 1: Calculate 7.89 × 3.21 = 25.3269
• Step 2: Instead of typing 25.3269 ÷ 2, just press ANS ÷ 2

This helps you avoid rounding errors in the middle of calculations.

Table function

Some calculators have a table mode. This is useful when you need to work out several values of an expression (like filling in a table for graph plotting). Instead of typing the expression multiple times, you can:

1. Enter the expression once
2. Let the calculator work out all the values automatically

This saves time and reduces mistakes.