Question 1

How do I find the radius from the area?

Accepted Answer

Rearrange A = πr² to r = √(A ÷ π). An area of 50 gives r ≈ 3.99.

Question 2

How do I find the radius from the circumference?

Accepted Answer

r = C ÷ (2π). A circumference of 100 gives r ≈ 15.92.

Question 3

Why is π irrational?

Accepted Answer

Johann Lambert proved in 1761 that π cannot be written as a fraction, so its decimal digits never end or repeat.

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