Outside edge length of a circle. 2π^r.
The circumference is the total distance around the outside edge of a circle.
where is the radius.
Circumference appears in problems involving circles, arc length, and geometry applications. Recognizing the formula and how it connects to radius and diameter allows for quick, accurate calculations.
Distance from center of circle to a point on the edge.
Key Idea: Radius
The radius of a circle is the distance from the center of the circle to any point on its edge.
General Rule:
All radii (plural of radius) in a circle are equal in length.
The diameter is twice the radius (d=2r).
The radius is used in formulas for circumference (C=2πr) and area (A=πr^2).
Why this matters for the SAT:
Understanding radius helps you quickly apply circle formulas and solve geometry problems involving area, circumference, and distance within circles.
–
–
