Area of Circles Flashcards

The area of a circle is calculated using the formula A = πr², where r is the radius.

The distance from the centre of a circle to any point on its circumference.

The distance across a circle through its centre. It is twice the radius (d = 2r).

A mathematical constant approximately equal to 3.14159, used in calculations involving circles.

The radius is half the diameter (r = d/2).

The area is measured in square units, such as cm², m², etc.

Rearrange the formula A = πr² to r = √(A/π) to find the radius when the area is given.

The area of a semicircle is half the area of a full circle: A = ½πr².

The area of a quarter circle is one-fourth the area of a full circle: A = ¼πr².

Always ensure the radius is used in the formula, not the diameter. If given the diameter, divide it by 2 to find the radius.