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Math Help - vectors

  1. #1
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    Post vectors

    Find the smallest interior angle of the triangle ABC whose vertices are given:-

    A = (3,1,-2) B = (3,0,-1) C = (5,2,-1)

    I am not sure what to do here...i tried using the dot product but it didnt workout...any help??
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  2. #2
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by omibayne View Post
    Find the smallest interior angle of the triangle ABC whose vertices are given:-

    A = (3,1,-2) B = (3,0,-1) C = (5,2,-1)

    I am not sure what to do here...i tried using the dot product but it didnt workout...any help??
    Find vector equations that represent the line segments that connect the three points. Then find the angle between them using the formula:

    \cos\vartheta=\frac{\bold u\cdot\bold v}{||\bold u|| ||\bold v||}\implies\vartheta=\cos^{-1}\left(\frac{\bold u\cdot\bold v}{||\bold u|| ||\bold v||}\right)

    --Chris
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  3. #3
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    Quote Originally Posted by Chris L T521 View Post
    Find vector equations that represent the line segments that connect the three points. Then find the angle between them using the formula:

    \cos\vartheta=\frac{\bold u\cdot\bold v}{||\bold u|| ||\bold v||}\implies\vartheta=\cos^{-1}\left(\frac{\bold u\cdot\bold v}{||\bold u|| ||\bold v||}\right)

    --Chris
    yeah i didnt find the equations for line segments....anyways thanks a lot for ur help
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