Frequently Asked Questions
What is the formula for the area of a circle?
Area = π × r², where r is the radius. For a circle with radius 5: area = π × 25 ≈ 78.54 square units.
What is the formula for circumference?
Circumference = 2 × π × r = π × d. For diameter 10: circumference = 10π ≈ 31.42 units.
What is the difference between radius and diameter?
Radius is the distance from center to any point on the circle. Diameter is the distance across through the center. Diameter = 2 × radius.
What is pi (π)?
Pi ≈ 3.14159265... is the ratio of circumference to diameter. It's irrational — its decimals never end or repeat.
How do I find the radius from the area?
r = √(Area / π). For area = 50: r = √(50/π) ≈ 3.99.
How do I find the diameter from circumference?
d = C / π. For C = 31.42: d = 31.42/π ≈ 10.
What is a sector of a circle?
A sector is a pie-shaped region bounded by two radii and an arc. Area = (θ/360°) × π × r².
How accurate are the calculations?
Uses JavaScript's Math.PI (15+ significant digits). Results shown to 4 decimal places — sufficient for virtually all practical uses.