Unit 5
Glossary
Accelerated 6
area of a circle
The area of a circle is the number of square units it covers. If a circle has radius
For example, a circle has radius of 3 inches. Its area is
circle
A circle is made of all the points that are the same distance from a given point. That given point is the center of the circle.
Every point on this circle is 5 cm away from point
circumference
The circumference of a circle is the distance around the circle. If a circle has radius
For example, a circle has a radius of 3 inches. Its circumference is
constant of proportionality
In a proportional relationship, the values for one quantity are each multiplied by the same number to get the values for the other quantity. This number is called the constant of proportionality.
In this example, the constant of proportionality is 3.
coordinate plane
The coordinate plane is one way to represent pairs of numbers. The plane is made of a horizontal number line and a vertical number line that cross at 0.
Pairs of numbers can be used to describe the location of a point in the coordinate plane.
Point
diameter
A diameter is a line segment that goes from one point on a circle to another and passes through the center. The length of this segment is also called the diameter. Every diameter of a circle is the same length.
origin
The origin is the point
pi (
There is a proportional relationship between the diameter and circumference of any circle. The constant of proportionality is pi. The symbol for pi is
This relationship can be represented with the equation
Some approximations for
proportional relationship
In a proportional relationship, the values for one quantity are each multiplied by the same number to get the values for the other quantity.
This table shows a proportional relationship between
| 2 | 8 |
| 3 | 12 |
| 5 | 20 |
| 10 | 40 |