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Diameter

Concept

Diameter

A diameter of a circle is a chord that passes through the center of the circle. Move points

A

and

B

to see when a chord becomes a diameter.

A circle with a movable chord to see when a chord becomes a diameter

On the other hand, the phrase the diameter of a circle refers to the length of any chord passing through the center of the circle.

A circle with a chord passing through the center

Furthermore, the diameter of a circle is exactly twice as long as its radius.

$d = 2r$