Unit 7.1 Equation of a Circle

(x - h)² + (y - k)² = r², where (h, k) is the center and r is the radius.

The radius is the distance from the center of the circle to any point on its circumference.

The diameter is twice the radius: Diameter = 2 * Radius.

C = π * d or C = 2 * π * r, where d is the diameter and r is the radius.

Area = π * r², where r is the radius.

A chord is a line segment whose endpoints lie on the circle.

A tangent is a line that touches the circle at exactly one point.

The circumference is directly proportional to the radius: C = 2 * π * r.

The center is the point that is equidistant from all points on the circle.

In the equation (x - h)² + (y - k)² = r², r is the square root of the number on the right side.