The diameter is the longest line which can be fitted inside a circle. It passes through the center of the circle. The distance around a circle is known as the circumference. Even though the diameter and circumference are different for different circles, the number pi remains constant: its value never changes. This is because the relationship between the circumference and diameter is always the same.
This diagram showing how PI can be found by using a circle with a diameter of one . The circumference of this circle is /Pi .
See This Nice Animated Video about Pi
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