Discovering the sum of the angles of a triangle

Discussion in 'General Education' started by Aliceacc, Sep 27, 2010.

  1. Aliceacc

    Aliceacc Multitudinous

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  3. mom2mikey

    mom2mikey Cohort

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    Sep 27, 2010

    You can also draw and cut out a bunch of differnet triangles and then "rip" off each corner and discover that they will always form a straight line (180 degree angle) when you place them side by side by side.
     
  4. comp

    comp Rookie

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  5. Aliceacc

    Aliceacc Multitudinous

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    I proved it today in class using alternate interior angles.

    But this was a whole lot more visual for kids who like to actually SEE it.
     
  6. Cerek

    Cerek Aficionado

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    That's how I've seen it done as well. It's really cool because, no matter what size or dimensions they make the triangle, when the "corners" are ripped or cut off, they will always make a straight line.

    The other model is very cool as well. Thanks for finding that, Alice. :thumb:
     
  7. Bumble

    Bumble Groupie

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    Thank you! This will help our upper grades.
     
  8. Marci07

    Marci07 Devotee

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    Isn't teaching geometry great? I love teaching geometry. It's so much fun.
     
  9. Hoot Owl

    Hoot Owl Aficionado

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    Wow!
     
  10. MissJill

    MissJill Cohort

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    That's what I have done in the past, works great!
     
  11. CindyBlue

    CindyBlue Cohort

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    How'd you do this?? Sounds great!
     
  12. Aliceacc

    Aliceacc Multitudinous

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    Draw a line parallel to the base of the triangle, through the other vertex.

    Then mark off the congruent alternate interior angles, one to the first vertex of the triangle, and another to the second.

    Now add the 3 angles near that top vertex-- they add up to a straight angle.
     

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