Everything Maths Grade 10

5.5 Calculator skills EMA3R

In this section we will look at using a calculator to determine the values of the trigonometric ratios for any
angle. For example we might want to know what the value ofsin 55 ◦is or what the value ofsec 34 ◦is.

When doing calculations involving the reciprocal ratios you need to convert the reciprocal ratio to one of the
standard trigonometric ratios:sin,cosandtanas this is the only way to calculate these ratios on your calculator.

IMPORTANT!

Most scientific calculators are quite similar but these steps might differ depending on the calculator you use.
Make sure your calculator is in “degrees” mode.

NOTE:

Note thatsin^2 = (sin)^2. This also applies for the other trigonometric ratios.

Worked example 2: Using your calculator

QUESTION

Use your calculator to calculate the following (correct to 2 decimal places):

1.cos 48 °

2. 2 sin 35 °
   3.tan^281 °


3. 3 sin^272 °
   5.^14 cos 27 °
   6.^56 tan 34 °
   7.sec 34 °
   8.cot 49 °

SOLUTION

Step 1:

The following shows the keys to press on a Casio calculator. Other calculators work in a similar way. On a

Casio calculator ( is automatically added after pressingsin,cosandtanso you just need to press ) after

typing in the angle to close the brackets.

1.Press cos 48 ) = 0,66913...0,67

2.Press 2 sin 35 ) = 1,147152...1,15

3.Press ( tan 81 ) ) x^2 = 39,86345...39,86

OR

Press tan 81 ) = ANS x^2 ANS = 39,86345...39,86

4.Press 3 ( sin 72 ) ) x^2 = 2,71352...2,71

OR

Press sin 72 ) = ANS x^2 = ANS  3

116 5.5. Calculator skills