Find the area and circumference of a circle. Find the radius or diameter of a circle when given the area of circumference?

Area = πr²

Circumference = 2πr

Step-by-step explanation:

When given the radius r,

Area of a circle A = πr²

Circumference of the circle C = 2πr

When given diameter d,

Area of a circle A = πd²/4

Circumference of a circle = πd

To find the radius r and d from area A,

r = sqrt (A/π)

d = sqrt (4A/π)

To find the radius r and diameter d from a given circumference C,

r = C / (2π)

d = C/π

Where d = 2r