The diameter of a circle is a straight line segment that passes through the center of the circle and has its endpoints on the circle's boundary. It is the longest chord of the circle and divides the circle into two equal halves
. The length of the diameter is twice the radius of the circle. If rrr is the radius, then the diameter ddd is given by:
d=2rd=2rd=2r
Conversely, the radius is half the diameter:
r=d2r=\frac{d}{2}r=2d
The diameter is often denoted by the letter ddd or the symbol ∅\varnothing ∅ (phi), especially in engineering and technical drawings
. In summary:
- The diameter is the distance across the circle through its center.
- It connects two points on the circle's edge.
- It is twice as long as the radius.
- It is related to the circumference CCC by the formula:
C=πdC=\pi dC=πd
This means the diameter is a fundamental measure of a circle's size, used to calculate other properties like circumference and area
