Are my postulates true regarding circles?

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SUMMARY

The discussion centers on the mathematical relationship between the radius and circumference of a circle, specifically addressing the impossibility of having both a rational circumference and a rational radius. The participants assert that knowing the exact radius of a circle precludes knowing its exact circumference, and vice versa, due to the nature of π (pi) as an irrational number. This concept, while not new, emphasizes the limitations of finite decimal representation in mathematics.

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  • Familiarity with the concept of irrational numbers, particularly π (pi).
  • Knowledge of mathematical representation and decimal sequences.
  • Basic principles of rational and irrational relationships in mathematics.
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student34
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If we know the exact radius of a circle, then we can't have an exact circumference, and if we know the exact circumference, then we can't know the exact radius.

If these postulates are true, then I realize that this idea is not original but probably known since B.C.
 
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Exact isn't the right word to use. If I have a circle with diameter 1, I know that the circumference is exactly ##\pi##, I just can't represent ##\pi## by a finite decimal sequence.

However you are right in your idea, a circle cannot simultaneously have a rational circumference and a rational radius.
 

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