Radius Study Guide

The radius of a circle is the distance from the center of the circle to any point on its circumference. It is a fundamental measurement in geometry and is used in various mathematical calculations involving circles.

Key Concepts

• Definition: The radius of a circle is a line segment from the center of the circle to any point on its circumference.
• Symbol: The radius is commonly denoted by the letter "r".
• Measurement: The length of the radius can be measured in units such as centimeters, inches, or meters.
• Relationship with Diameter: The radius is half the length of the diameter of a circle.

Formulas

There are several important formulas involving the radius of a circle:

• Calculate Circumference: The circumference of a circle can be calculated using the formula:
  C = 2πr
• Calculate Area: The area of a circle can be calculated using the formula:
  A = πr²

Practice Problems

Here are some practice problems to test your understanding of the radius:

1. Find the radius of a circle with a circumference of 12π.
2. If the radius of a circle is 5 cm, calculate its area.
3. What is the diameter of a circle with a radius of 8 inches?

Remember, the key to mastering the concept of radius is to practice using it in various calculations and problems involving circles.

Now that you have a solid understanding of the radius of a circle, you can confidently apply this knowledge to solve geometry problems and understand the properties of circular shapes.