Results 1 to 2 of 2

Math Help - Help me find Arccot please!

  1. #1
    Junior Member
    Joined
    Jun 2005
    Posts
    43

    Help me find Arccot please!

    I am trying to solve a question involving inding the Arccot. I've inserted a link and an image file. It's my first time doing this...hope it works. http://www.mathhelpforum.com/math-he...ntid=108&stc=1.

    Attached Thumbnails Attached Thumbnails Help me find Arccot please!-trigquestion.jpg  
    Last edited by coopsterdude; August 14th 2005 at 02:52 PM. Reason: Image not showing
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Apr 2005
    Posts
    1,631
    Is that correct, sqrt(3/3) ?
    Why, sqrt(3/3) is sqrt(1). And sqrt(1) is +,-1.
    So, arccot[sqrt(3/3)] = arccot(+,-1)
    And so, arccot[-sqrt(3/3)] = arccot[-(+,-1)] = arccot(-,+1) = arccot(+,-1)

    Cotangent (and Tangent) function is positive in the 1st and 3rd quadrants,
    So, Arccot (1) is 45 or 225 degrees. Or, pi/4 and 5pi/4 radians.

    Cotangent (and Tangent) function is negative in the 2nd and 4th quadrants,
    So, Arccot (-1) is 135 or 315 degrees. Or, 3pi/4 and 7pi/4 radians.

    Therefore, arccot[-sqrt(3/3)] = pi/4, 3pi/4, 5pi/4, or 7pi/4 radians in the interval [0,2pi]. -------answer.

    ----------------------

    However, I doudt if that is really sqrt(3/3)....

    --------------
    Addition....

    I think that is arccot[- (1/3)sqrt(3)]

    (1/3)sqrt(3) is actully 1/sqrt(3) if you rationalize the denominator.

    Hence the reference angle is 60 degrees or pi/3 radians,
    because cot(60deg) = 1/sqrt(3)

    Then, arccot[-(1/3)sqrt(3)] -----in the 2nd or 4th quadrants,
    = arccot[-1/sqrt(3)]
    = 120 or 300 degrees
    = 2pi/3 or 5pi/3 radians --------answer.
    Last edited by ticbol; August 15th 2005 at 03:40 AM.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. proof of arccot(x)
    Posted in the Calculus Forum
    Replies: 4
    Last Post: November 18th 2009, 03:04 AM
  2. Arccot series and Arithmetic progressions?
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: May 22nd 2009, 11:35 AM
  3. What is the derivative of arccot(e^2x)?
    Posted in the Calculus Forum
    Replies: 3
    Last Post: February 25th 2009, 08:54 AM
  4. quick help with arccot problem
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: November 6th 2008, 05:32 PM
  5. arccos(3/5)+arccot(1/7)
    Posted in the Trigonometry Forum
    Replies: 5
    Last Post: February 12th 2008, 01:02 PM

Search Tags


/mathhelpforum @mathhelpforum