Geometry

Math and Arithmetic

Algebra

# What area of circle using diameter instead of radius?

###### Wiki User

###### December 16, 2009 2:32AM

a=pi r²

a=pi (d/2)²

## Related Questions

###### Asked in Math and Arithmetic, Algebra, Geometry

### Diameter of a circle?

If you know the radius
Given the radius of a circle, the diameter can be calculated
using the formula:
The Diameter is Twice the Radius, or D = 2R
Where R is the Radius.
If you know the circumference
If you know the circumference of a circle, the diameter is found
using the formula D= C/π
where:
C is the circumference of the circle
π is Pi, approximately 3.142

###### Asked in Math and Arithmetic, Algebra, Geometry

### What is the formula for the circumference of a circle?

The circumference of a circle is the length around it. The
circumference of a circle can be calculated from its diameter using
the formula: Circumference of a circle = 2*pi*radius or
Circumference of a circle = pi*diameter
where r is the radius and d is the diameter of the
circle, and Ï� (the Greek letter pi) is defined as the ratio of the
circumference of the circle to its diameter.
(the numerical value of pi is 3.141 592 654 589 793...).
d * pi
or 2 * r * pi
Where d is diameter and r is radius and pi = 3.14159

###### Asked in Math and Arithmetic, Algebra, Geometry

### How do you find the area of the circle with no radius?

The circle must have a radius. If you do not know it then you
find out the area using the diameter, (this is the length of two
points directly across from each other on the circle.
The equation for the area of a circle when using the diameter =π
× (d/2)²
By the way, π is approximately = 3.14159265. or 22/7
A circle with no radius has no area and is sometimes
considered by certain branches of geometry and topology as a
point.