# 10.5.1 Calculator Exploration: Introducing Pi

The calculator can be accessed on the left-hand side bar under Toolkit.

In this exploration, you will use the calculator for formulas involving

The calculator uses a 14-decimal place approximation for , precise enough for most calculations.

Find the key. It looks like this: . When you want to use in a calculation, just click on the key.

## Activity: Machine Components

Using the key on the calculator, work out the perimeters for each of the following machine components. Assume that the measurements are sufficiently accurate to allow answers to 2 decimal places.

### Comment

The formula for the circumference of a circle is . When you want to multiply by , click on the key.

(a) The circumference of the circle is (rounded to 2 decimal places).

(b) The radius of the circle is 3.2 in., so the circumference is (rounded to 2 decimal places).

### Comment

Break this more complicated shape up into simpler shapes that you know how to calculate the circumference.

(c) The perimeter is made up of two semicircular ends of diameter 1.6 yards and two straight edges of length 2 yards.

The two semicircular ends together form a circle, so the distance around the ends of the component will be the same as the distance around a circle of diameter 1.6 yards.

This distance = . Then total distance round the edge of the component = (rounded to 2 decimal places).

## To recap:

• When you want to use in a calculation, use the key on the calculator.
• The circumference of a circle is its perimeter.
• To calculate the circumference you can use one of two formulas:

10.5.2 Protecting an Old Tree