Using a Calculator

Why are calculator skills important?

GCSE Mathematics uses many of the special functions of a scientific calculator
- To answer questions successfully you need to be able to use your calculator effectively
You may need to use some of the functions on the calculator in other subjects such as Science
There are many different models of calculator
- Any scientific calculator will have the functions you need but may be accessed in different ways
- You need to know how to use the features on your specific model
If you have an old or very basic scientific calculator the functions may be used backwards
- To find the sine of an angle on a newer calculator, type sin (57)
- On an older calculator you may need to type 57 then press the sin button
The notes below apply to most if not all scientific calculators but the images are based on the Casio fx-83GT

Calculator

The Casio fx-83GTX Classwiz

How do I make sure that I have the correct settings on the calculator?

Check you know how change the mode of your calculator
- There is usually a button marked 'MODE'
- Most calculators default to 'MATH' mode with the word MATH written across the top of the display or using a symbol
The 'Angle Unit' needs to be degrees
- There is usually a button marked 'SETUP' where you can find the angle unit options
- A 'D' symbol at the top of the display is used to indicate that the calculator is in the degrees setting
Make sure you can switch between 'exact' answers (e.g. fractions) and 'approximate' answers (e.g. decimals)
- When in 'MATH' mode press the 'S $\Leftrightarrow$ D' button to switch between answer types

What are the shortcut buttons on the calculator?

There are several very useful shortcut buttons on the calculator that you should know
- The fraction, square, cube, power and square root buttons are all frequently used
- Use the 'SHIFT' (2^nd or INV) button to access functions including mixed numbers, cube roots, and n^th roots

Calculator shortcut buttons

Why is using brackets important?

Applying brackets correctly on your calculator helps you to avoid errors in your calculations
- Use brackets as you would in written mathematics
- Put brackets around negative numbers in calculations
  - Remember, $- 3^{2}$ gives you a different result to ${(- 3)}^{2}$
  - Use the '(-)' button for negative values, not the minus button

Which buttons are useful for trigonometry?

Use the sin, cos and tan buttons when finding missing sides of a triangle
- Remember to make sure that your calculator is in degrees mode
Use sin^-1, cos^-1 and tan^-1 when finding missing angles of a triangle
- Access these by using the 'SHIFT' button
When using a trig function, the calculator gives you an open bracket '('
- Remember to use a closed bracket ')' after typing the angle in

Which buttons are useful for standard form and calculations involving π?

To write a number in standard form on the calculator, use the ×10^x
- Modern calculators display standard form in the way it is written, e.g., 2 x 10⁵
- Older models may use a small capital letter 'E' in place of ×10^x, e.g., 2E5
is often near the standard form button
- You may need to use the 'SHIFT' button to access it

What is the Ans function?

The Ans (answer) button recalls the last answer the calculator calculated
- Use this when working with decimals in the middle of solutions to avoid rounding until your final answer

What is the table function?

If your calculator has a table function or mode it can be used in 'complete the table of values and draw the graph' type questions
- This can help you to reduce the number of calculations you have to do
- It can also help to reduce errors

Exam Tip

Get a calculator early and learn how to use all the essential functions
When using your calculator in an exam do one calculation at a time
- Make sure you write down on paper each calculation that you do
- Always write down more digits than the final answer requires in your working
- Only round your final answer

Worked example

(a)

Use your calculator to work out

$\frac{\sqrt{4.69}}{0 . 34^{3} + \sin (45 °)}$

Give your answer as a decimal.
Write down all the figures on your calculator display.

Type the calculations in the numerator and the denominator into your calculator separately
Write down the decimal answers
Use '...' to show that you have not rounded them
You need to show this working to get full marks

$\sqrt{4.69} = 2.165 64 . . .$

$0 . 34^{3} + \sin (45) = 0.746 410 . . .$

Type the whole calculation into your calculator in one go
Use the fraction button, square root button, cube button and remember to close the bracket after the sine function

$2.901406085$

(b)

Given that

a = p^{2} q

Find the value of

a

when

p = 1.2 \times 10^{- 3}

and

q = 7.83 \times 10^{5}

.
Give your answer to 3 significant figures.

Substitute in the values for p and q
Write down your calculation to show your working

$a = p^{2} q a = {(1.2 \times 10^{- 3})}^{2} \times (7.83 \times 10^{5})$

Enter the calculation into your calculator and write down all the digits on your calculator display

$a = 1.12752$

Round to 3 significant figures

$a = 1.13$ (3 s.f.)

(c)

Complete the table of values for $y = 6 x + 1$ .

$x$	-3	-2	-1	0	1	2	3
$y$		-11					19

Use brackets around negative values and the '(-)' button

$6 \times (- 3) + 1 = - 17$

Use arrow keys to go back to the input line and change each '-3' to '-1'

$6 \times (- 1) + 1 = - 5$

Repeat for each of the remaining values in the table, 0, 1 and 2

$6 \times 0 + 1 = 1 6 \times 1 + 1 = 7 6 \times 2 + 1 = 13$

Alternatively, use the 'Table' mode/feature if your calculator has one

Complete the table with the values

$x$	-3	-2	-1	0	1	2	3
$y$	-17	-11	-5	1	7	13	19

Using a Calculator (Edexcel GCSE Maths: Foundation)

Revision Note