During the lecture, the neurologist explained how the circles of Willis provide collateral blood flow to the brain.

During circle time, the teacher reads a story and the children share their thoughts.

During our classroom circle times, students share stories, songs, and ideas.

In the geometry seminar, the professor compared the properties of several circumscribed circles drawn around different triangles.

The triangle's circumscribed circle passes through all three vertices.

To find the inscribed circle of the triangle, calculate the intersection point of the angle bisectors and then draw the circle tangent to all three sides.

The mathematician drew several inscribed circles to illustrate the theorem.

After the photo finish, the jockey led the exhausted champion into the winner's circle for the trophy presentation.

Geometry students studied the circles of Apollonius to understand loci defined by distance ratios.

In classical inversive geometry, a circle inversion with center O and radius r maps any point P ≠ O to the point P' on the ray from O through P for which OP × OP' = r², and maps O to the point at infinity.