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-   -   Trigonometry equation (https://www.askmehelpdesk.com/showthread.php?t=371732)

  • Jul 3, 2009, 05:31 PM
    lucky_girl
    trigonometry equation
    Solve each equation for principle angle values (where reasonable) or principle
    angle inverse trigonometric functions at the proper point


    1.2cosē(x)+cos(x)-1=0

    2.sin(3x)=cos(3x)
  • Jul 3, 2009, 05:56 PM
    Perito
    Quote:

    Solve each equation for principle angle values (where reasonable) or principle
    angle inverse trigonometric functions at the proper point

    1.2cosē(x)+cos(x)-1=0

    2.sin(3x)=cos(3x)
    1. This is solved just like an ordinary equation. Try a simple substitution, Y = cos(x).



    becomes



    You can solve this using the quadratic equation:



    And substitute back into the equation



    Then



    2.




  • Jul 3, 2009, 09:49 PM
    lucky_girl

    thank you so much...

    I did 2nd one like this

    sin3(0)=cos3(0)
    tan3(0)=1
    3(0)=45 degrees
    0 = 15 degrees

    am I right?
  • Jul 4, 2009, 04:41 AM
    Perito

    Quote:


    i did 2nd one like this

    sin3(0)=cos3(0)
    tan3(0)=1
    3(0)=45 degrees
    0 = 15 degrees

    am i right?
    This doesn't look like the second one you gave me. You had written "sin(3x)", including the parentheses. Now you're writing Sin3(0). Where did the "0" come from and is this or is it ? I'll assume the "0" is a typo and that the 3 comes inside the parentheses:









    Then you are correct.
  • Jul 4, 2009, 08:46 AM
    Unknown008

    LOL! I reckon the OP mean theta
  • Jul 4, 2009, 09:05 AM
    Perito

    Some of these things zoom over my head.

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