Results 1 to 2 of 2

Math Help - TRIG: inverses

  1. #1
    Newbie
    Joined
    Nov 2008
    Posts
    1

    TRIG: inverses

    Hello-
    I am currently working on a problem and I don't completely understand how to get to the correct answer.
    The problem is:
    find exact value of:

    sin-1[cos(-2pi over 3)]

    (sorry, I haven't figured out how to manipulate text.)

    I figure that it's -radical 3 over 2; -pi over 3. The book says it -pi over 6. I see that cos radical 3 over 2 is pi over 6, but sin radical 3 over 2 is pi over 3. (?)
    Please help.
    Thanks.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,621
    Thanks
    426
    from the unit circle (which you know well, correct?)

    \cos\left(-\frac{2\pi}{3}\right) = -\frac{1}{2}

    now ...

    \sin^{-1}\left(-\frac{1}{2}\right) = -\frac{\pi}{6}
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Inverses of (f o g)(x) (g o f)(x)
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: May 11th 2011, 01:24 PM
  2. Inverses
    Posted in the Advanced Algebra Forum
    Replies: 3
    Last Post: May 2nd 2010, 04:34 AM
  3. Right inverses
    Posted in the Math Topics Forum
    Replies: 2
    Last Post: November 19th 2008, 11:38 AM
  4. inverses......
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: May 24th 2008, 04:12 AM
  5. Inverses
    Posted in the Calculus Forum
    Replies: 6
    Last Post: December 10th 2007, 04:37 AM

Search Tags


/mathhelpforum @mathhelpforum