Results 1 to 3 of 3

Math Help - trig identity question

  1. #1
    Newbie
    Joined
    Mar 2010
    Posts
    9

    Post trig identity question

    hey

    need some help with this one please..

    i need to prove that cot^2 \theta - cos^2 \theta = cot^2 \theta cos^2 \theta

    i took the right hand side and tried to do a similar thing to my text book in proving the question...

    this is what I got

    cot^2 \theta cos^2 \theta = (cos^2 \theta - cos^2 \theta.sin^2 \theta) \over(sin^2 \theta)

    \rightarrow cos^2 \theta\over sin^2\theta - cos^2 \theta \dot sin^2\theta \over sin^2 \theta

    \rightarrow RHS = LHS

    first of all is this correct? and second of all what rule gives me my first line?

    many thanks
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    Joined
    Jun 2009
    Posts
    806
    Thanks
    4
     cot^2\theta - cos^2\theta = \frac{cos^2\theta}{sin^2\theta} - cos^2\theta

    When you simplify you get the first line.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member grgrsanjay's Avatar
    Joined
    May 2010
    From
    chennai,tamil nadu
    Posts
    143
    Thanks
    1
    cot^2\theta cos^2\theta  =
     = \frac{cos^2\theta  cos^2\theta}{sin^2\theta} =   \frac{cos^2\theta (1 - sin^2\theta)}{sin^2\theta}
    Last edited by grgrsanjay; August 13th 2010 at 07:04 PM.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. another trig identity question
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: April 9th 2010, 09:41 PM
  2. Simple Trig Identity Question
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: September 9th 2009, 11:02 PM
  3. Trig identity question
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: May 14th 2009, 12:33 PM
  4. Trig identity question!
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: February 8th 2009, 08:05 AM
  5. Little trig identity question.
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: September 17th 2008, 02:06 PM

Search Tags


/mathhelpforum @mathhelpforum