# Question Video: Identifying all the Radii in a Given Circle Mathematics • 11th Grade

Identify all the radii in the following circle.

01:40

### Video Transcript

Identify all the radii in the following circle.

The word radii is just a plural of the word radius. So weโre being asked to find all of the lines in the diagram, which are a radius of the given circle. Recall that the radius of a circle is any line which joins the center of the circle to a point on the circumference. The center of the circle weโve been given is the point ๐. So any line which connects ๐ to the circumference will be a radius of this circle.

First, we note that the line segment ๐๐ต is a radius of the circle as ๐ is the center and ๐ต is a point on the circumference. The line segment ๐๐ถ is also a radius of the circle, as is the line segment ๐๐ธ. Finally, we note that the line segment ๐๐น is also a radius of this circle. So weโve identified four line segments which are radii of this circle, ๐๐ต, ๐๐ถ, ๐๐ธ, and ๐๐น.

Letโs just have a brief look at what some of the other line segments in this circle are called. The line segments ๐ต๐ธ and ๐น๐ถ are diameters of the circle because they each join two points on the circumference of the circle and pass through the circleโs center. The line segment ๐น๐ท is a chord of the circle because it joins two points on the circumference but doesnโt pass through the center of the circle.

We need to be aware of the different types of lines that exist within circles. These lines are radii, diameters, and chords, all of which weโve seen examples of in this question.