Parts of a Circle

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

The diameter is the distance across the circle through its center, equal to twice the radius.

The circumference is the total distance around the circle.

Circumference can be calculated using the formula: $$C = 2\text{π}r$$ or $$C = \text{π}d$$ .

The area of a circle is calculated using the formula: $$A = \text{π}r^2$$ .

π (pi) is a constant approximately equal to 3.14, representing the ratio of the circumference of a circle to its diameter.

The diameter is 4 cm, since diameter = 2 × radius.

The radius is 5 cm, since radius = diameter / 2.

The diameter is always twice the length of the radius.

Area = $$\text{π} \times (3)^2 = 9\text{π} \text{ cm}^2$$ .