Circular arc

Part of a circle’s boundary, characterized by its radius and a certain angle.

Circular sector

Part of a disk bounded by two radii and a circular arc.

Circular segment

A region of a circle which is “cut off” from the rest of the circle by a secant or a chord.

Circumcircle

The circumcircle of a polygon is the circle that passes through all of its vertices.

Circumference

The perimeter of a circle or ellipse.

Cone

A three-dimensional object with a flat base (mostly a circle) that tapers linearly to its apex point. The volume is 1/3 times base area times height.

Congruent

Two objects are congruent of they have the same shape and size.

Cosine rule

Relation between triangle side lengths and one of its angles: c2=a2+b2-2abcosγ.

Cyclic quadrilateral

A quadrilateral whose vertices all lie on a single circle. In it, opposite angles add up to 180°.

Derivative

Measures the sensitivity to change of a function output with respect to a change in its input.