What is a circle?
Answer
A circle is the set of all points in a plane that are at a fixed distance, called the radius, from a fixed point called the centre.
The working
Definition
Every point on a circle lies at the same distance from its centre. This constant distance is the radius.
Key parts
The centre is the fixed midpoint, the radius is the distance from centre to any point, and the diameter is a chord through the centre equal to twice the radius.
Equation form
A circle with centre (h, k) and radius r has the equation (x − h)² + (y − k)² = r². Centred at the origin it becomes x² + y² = r².
Measurements
Its boundary length is the circumference C = 2πr, and the space enclosed is the area A = πr².
Example
A circle of radius 7 cm has circumference 2 × (22÷7) × 7 = 44 cm and area (22÷7) × 7² = 154 cm².
Stuck on something else?
Type your own doubt into the solver and get the full working in seconds — free, for physics, chemistry, maths and biology.
Open the solverRelated doubts