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## Geometry (all content)

### Course: Geometry (all content)>Unit 7

Lesson 8: Area and circumference of circles

# Labeling parts of a circle

Radius, diameter, center, and circumference--all are parts of a circle. Let's go through each and understand how they are defined. Created by Sal Khan and Monterey Institute for Technology and Education.

## Want to join the conversation?

• What is the center?
• Imagine radii One end point is on the circumference. The other point is shared by all the radii and is equidistant from any point on the circumference and. IS called the centre of the circle
• why is half of the diameter called the radius
• it not the line through the circle is the diameter and the radius is half of the circle
• I hate circle!
• same
• at what dont undertsand bro
• The circumference of a circle is basically the distance around a circle. For example, if you had a park or other outdoor area that was shaped in a perfect circle, and you walked all the way around the edge of it, you would have walked along the circumference of the circle. Basically, you can think of the circumference as the perimeter of a circle.
• I am confused why do we use pi in this equation
• I think that's because almost all equations (if not all) relating to circles use pi
• why do we need to learn this?
• how do you find the diameter, radius, and the circumference of a circle
• The circumference of a circle is equal to pi times the diameter. The diameter is two times the radius, so the equation for the .circumference of a circle using the radius is two times pi times the radius.
Solve the equation for the diameter of the circle, d= C/π. In this example, "d = 12 / 3.14." or "The diameter is equal to twelve divided by 3.14." Divide the circumference by pi to get the answer. In this case, the diameter would be 3.82 inches.