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 #5
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Apr 23, 2023
Apr 22, 2023
 #3
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Try this: 

 

Let's call the two points A and B, and let O be the center of the circle.

 

Without loss of generality, we can assume that point A is located at the top of the circle. Then, the distance between point A and any other point B on the circle is given by the length of the arc subtending angle AOB.

If we fix point A and randomly choose a point B, the probability that the distance between A and B is at most 1 is the same as the probability that angle AOB is less than or equal to 60 degrees (since the length of an arc subtending an angle of 60 degrees on a unit circle is 1).

 

So, let's assume that point A is located at (1, 0) and let's consider the region of the circle to the right of A. The probability that point B falls in this region is 1/2. To find the probability that the angle AOB is less than or equal to 60 degrees, we need to find the length of the arc that subtends this angle and divide it by the total circumference of the circle.

 

The length of the arc subtending angle AOB is just the length of one-sixth of the circumference of the circle (since angle AOB is 60 degrees and there are 6 such angles in a full circle). The circumference of the circle is 2π, so the length of the arc is (1/6) * 2π = π/3. Therefore, the probability that the distance between the two points is at most 1 is:

(1/2) * (π/3) / (2π) = 1 / 12

 

So the probability that the distance between the two points is at most 1 is 1/12.

 

P. S. I did it in another way and got: 3 / 4. But was less sure of that method!

Apr 22, 2023

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