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Home > Probability
Four Points in a Square (Posted on 2023-01-12) Difficulty: 4 of 5
Four points are chosen at random inside a square. Each point is chosen by choosing a random x-coordinate and a random y-coordinate.

A convex quadrilateral is drawn with the the four random points as the vertices.

Determine the probability that the center of the square is inside this quadrilateral.

See The Solution Submitted by K Sengupta    
Rating: 5.0000 (3 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Sanity check on classification | Comment 7 of 10 |
(In reply to re(2): preliminary simulation results by Charlie)

As a sanity check these show situations where the random points were deemed as forming a quadrilateral that is either convex or non-conves, and if convex, whether it contains the center of the square.

The center of the square is marked with 4 x's (the square is 60 character positions high and 100 wide, so there's no center character). The random points are marked with *'s. There are some close calls, so the coarseness of the grid can make it difficult to see in some instances.



Found to be convex and to contain the center of the square:

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K>> 

Found to be non-convex:
 
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K>> 

Determined as convex but not containing center of square:
 
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  Posted by Charlie on 2023-01-13 08:27:53
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