Chapter 4.3, Problem 31E

(a)

To determine

The value of $\sin 10°$ using a calculator and round it to four decimal places.

Answer to Problem 31E

The value of $\sin 10°$ is $0.1736$ .

Explanation of Solution

Given:

The trigonometric identity is $\sin 10°$ .

Calculation:

The value of $\sin 10°$ can be calculated by graphical calculator.

Steps to calculate the values using a graphical calculator is as follows.

1. Start calculator and press the “Y” button to enter the function screen.
2. Type the trigonometric function to calculate its value.
3. Press “Enter” to show the result.

So, the value of $\sin 10°$ using the calculator is,

  $\sin 10°=0.173648177$

Round off the answer to four decimal places as $0.1736$ .

Therefore, $\sin 10°=0.1736$ .

(b)

To determine

The value of $\cos 80°$ using a calculator and round it to four decimal places.

Answer to Problem 31E

The value of $\cos 80°$ is $0.1736$ .

Explanation of Solution

Given:

The trigonometric identity is $\cos 80°$ .

Calculation:

The value of $\cos 80°$ can be calculated by graphical calculator.

Steps to calculate the values using a graphical calculator is as follows.

4. Start calculator and press the “Y” button to enter the function screen.
5. Type the trigonometric function to calculate its value.
6. Press “Enter” to show the result.

So, the value of $\cos 80°$ using the calculator is,

  $\cos 80°=0.173648177$

Round off the answer to four decimal places gives $0.1736$ .

Therefore, $\cos 80°=0.1736$ .