Results 1 to 2 of 2

Math Help - Trig identity

  1. #1
    Junior Member
    Joined
    Dec 2008
    Posts
    70

    Trig identity

    Hi,
    Have this problem not sure if i've answered the question or not?

    Verify the identity; (secA - 1) / (secA +1) + (cosA -1) / (cos A + 1) = 0

    i changed secA into 1/cosA then re arrange and manipulated the LHS so at the end i get 1 - cos^2(x) = 1 - cos^2(x) or that the lhs had = 0 but not sure if i have properly answered the question?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    11,786
    Thanks
    1570
    Quote Originally Posted by monster View Post
    Hi,
    Have this problem not sure if i've answered the question or not?

    Verify the identity; (secA - 1) / (secA +1) + (cosA -1) / (cos A + 1) = 0

    i changed secA into 1/cosA then re arrange and manipulated the LHS so at the end i get 1 - cos^2(x) = 1 - cos^2(x) or that the lhs had = 0 but not sure if i have properly answered the question?
    \frac{\sec{A} - 1}{\sec{A} + 1} + \frac{\cos{A} - 1}{\cos{A} + 1} = \frac{\frac{1}{\cos{A}} - 1}{\frac{1}{\cos{A}} + 1} + \frac{\cos{A} - 1}{\cos{A} + 1}

     = \frac{\frac{1 - \cos{A}}{\cos{A}}}{\frac{1 + \cos{A}}{\cos{A}}} + \frac{\cos{A} - 1}{\cos{A} + 1}

     = \frac{1 - \cos{A}}{1 + \cos{A}} + \frac{\cos{A} - 1}{\cos{A} + 1}

     = \frac{1 - \cos{A} + \cos{A} - 1}{1 + \cos{A}}

     = \frac{0}{1 + \cos{A}}

     = 0.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Trig Identity?
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: December 13th 2010, 09:24 PM
  2. Trig identity, tan(2A)
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: March 12th 2010, 10:04 AM
  3. trig identity
    Posted in the Calculus Forum
    Replies: 1
    Last Post: September 15th 2009, 10:07 AM
  4. trig identity
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: May 25th 2009, 11:44 AM
  5. trig identity
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: February 26th 2008, 07:44 PM

Search Tags


/mathhelpforum @mathhelpforum