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Trigonometry Triangle Help

  1. Aug 22, 2007 #1
    First off, I was just moved up a grade (about 2 week ago) and the class is studying trigonometry.

    1. The problem statement, all variables and given/known data
    I have a triangle:
    Hyp = 10m
    Opp = 4m
    Adj= Unknown
    Feta = Unknown

    And I need to find feta.

    2. Relevant equations

    3. The attempt at a solution
    Well, I have tried a lot of random things lol.
    E.g: sin-1 (10x4)

    Well, thats actually about it.

    I also have another question. Exactly from the revision sheet.
    By using a radar beam. an observer at A determinses that a plane at B is 2000 metres away (AB=2000) Use the information given to calculate the height of the plane above the horizontal [tex]\overline AC[/tex] The angle is 50 degrees. I know the answer is 2000xsin 50, but how do I know t is sin? The teacher gave me the answer, but I dunno how she came up with sin :(

    Please help,

    Last edited: Aug 22, 2007
  2. jcsd
  3. Aug 22, 2007 #2


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    Staff Emeritus
    Science Advisor

    In order to do that, you first need to know the definitions of sine, cosine, etc!

    sine is defined, in a triangle,as "opposite/hypotenuse", NOT "opposite times hypotenuse. You need to find sin-1(4/10).
  4. Aug 22, 2007 #3
    4/10 thank you!!!!!!!! I was using 4x10. Completely forgot.

    Thankl you,

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