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Math Help - find the probability

  1. #1
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    find the probability

    randomly select three positive number a,b,c, and form a triangle with sides with lengths a,b,c.

    what is the probabiliy that this triangle has an angle > 90 degrees?
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  2. #2
    Member Ruun's Avatar
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    Hi!

    I'm gonna shoot in the dark... but here are my two cents:

    Supose that the triangle has an angle \theta\ < 90. Then you're done.

    In other case the other the sum of the other angles \theta_1+\theta_2<90 so they can't be greather than 90.

    ¿Then the probability is 1? Not sure
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  3. #3
    MHF Contributor arbolis's Avatar
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    If a=b=c then the angles are worth 60° so I'd say the probability is not worth 1. But I might be wrong since a probability of 1 doesn't mean the event will occur.
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  4. #4
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    Quote Originally Posted by szpengchao View Post
    randomly select three positive number a,b,c, and form a triangle with sides with lengths a,b,c.

    what is the probabiliy that this triangle has an angle > 90 degrees?
    szpengchao,

    This is a poorly-stated problem and it is not possible to solve it without additional information. The reason is that you must specify some probability distribution in order to "randomly select three positive numbers a,b,c". Do you have more information about the numbers?

    (There is no probability distribution which makes all positive numbers "equally likely".)
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