The coolest fact in trigonometry that you learn way too late...

  1. Femme_physics

    Femme_physics 2,555
    Gold Member

    The coolest fact in trigonometry that you learn way too late....

    So I just spent the last 12 hours learning trig (occasional food breaks).

    I just want to share with you something really, really, really, really, awesome.


    Check this out, you're gonna be blown away

    The law of cosines, applied to a right triangle is c^2 = a^2+b^2 - 2abCosA Whereas A is equal to zero!!!

    So the law of cosines for a right triangle is, in fact, the Pythagorean theorm!!! Math is sooooooooo awesome. Why did it only take me the last quarter of the textbook to learn this fact???
     
  2. jcsd
  3. statdad

    statdad 1,455
    Homework Helper

    Re: The coolest fact in trigonometry that you learn way too late....

    Perhaps I'm missing something here, but if A = 0, cos A = 1, and your statement comes in as

    [tex]
    c^2 = a^2 + b^2 - 2ab
    [/tex]

    which is not the Pythagorean Theorem.
     
  4. Femme_physics

    Femme_physics 2,555
    Gold Member

    Re: The coolest fact in trigonometry that you learn way too late....

    I mean, A is 90 degrees and therefor 0 is equal to 0!!!

    Sorry :blushing:
     
  5. Re: The coolest fact in trigonometry that you learn way too late....

    :biggrin:

    yep it's awesome
     
  6. Hurkyl

    Hurkyl 16,090
    Staff Emeritus
    Science Advisor
    Gold Member

    Re: The coolest fact in trigonometry that you learn way too late....

    Of course, this value is interesting too, as it's the theorem that if you have three collinear points:
    A --- B ---- C​
    Then the length of the whole (b) is the sum of the lengths of the two parts (a and c).
     
  7. statdad

    statdad 1,455
    Homework Helper

    Re: The coolest fact in trigonometry that you learn way too late....

    Don't worry - I had a feeling this is what you meant - but I wanted to make sure.

    You'll find lots of cool things in your math classes if you take the time to look around.
     
  8. Mark44

    Staff: Mentor

    Re: The coolest fact in trigonometry that you learn way too late....

    You don't need the law of cosines to conclude 0 = 0.
     
  9. Femme_physics

    Femme_physics 2,555
    Gold Member

    Re: The coolest fact in trigonometry that you learn way too late....

    Awesome link granpa! And thanks for the replies and humoring me :)
     
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