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    imorio is offline Senior Member
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    Default calculating the angle between 3 points

    I have 3 points: A, B and C. These are just pairs of doubles defining their x and y values. Now I need to calculate the angle between the lines AB and BC. Is there a methode in the standard java library that does this? I thought there was one in the Math class, but I was wrong.

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    Eranga is offline Moderator
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  3. #3
    JosAH's Avatar
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    Default

    Quote Originally Posted by imorio View Post
    I have 3 points: A, B and C. These are just pairs of doubles defining their x and y values. Now I need to calculate the angle between the lines AB and BC. Is there a methode in the standard java library that does this? I thought there was one in the Math class, but I was wrong.
    The dot product of two vectors AB and BC is defined as |AB|*|BC|* cos(a) where |x| is the length of vector x and a is the angle between the vectors AB and BC. The dot product also is AB_x*BC_x+AB_y*BC_y; do your math.

    kind regards,

    Jos
    cenosillicaphobia: the fear for an empty beer glass

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