Results 1 to 3 of 3

Math Help - Help with Trigonometric Identities

  1. #1
    Newbie
    Joined
    Oct 2010
    Posts
    2

    Help with Trigonometric Identities

    I need to solve the trig identity: (x stands for theta)
    1- (cos^2 x / 1 + sin x) = sin x

    I get the first step
    1 - ( 1 - sin ^ 2 x / 1 + sin x)
    And i dont understand the 3rd step

    1-(1-sin x)
    Can someone please explain to me how the third step is gotten?
    thanks
    Follow Math Help Forum on Facebook and Google+

  2. #2
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by mathmike View Post
    I need to solve the trig identity: (x stands for theta)
    1- (cos^2 x / 1 + sin x) = sin x

    I get the first step
    1 - ( 1 - sin ^ 2 x / 1 + sin x)
    And i dont understand the 3rd step
    1-(1-sin x)
    Can someone please explain to me how the third step is gotten?
    thanks
    yes, factor the numerator in your second step using the difference of two squares. that will cancel the denominator and give you what you want.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor harish21's Avatar
    Joined
    Feb 2010
    From
    Dirty South
    Posts
    1,036
    Thanks
    10
    \displaystyle {1 - \frac{cos^{2}x}{1+sinx} = 1 - \frac{1-sin^{2}x}{1+sinx} = 1 - \frac{(1+sinx)(1-sinx)}{1+sinx}= 1-(1-sinx) = sinx}

    note that:

    1-sin^{2}x = (1)^2 -(sinx)^2 = (1+sinx)(1-sinx)

    because

    (a)^2-(b)^2 = (a+b)(a-b)
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Trigonometric Identities
    Posted in the Trigonometry Forum
    Replies: 8
    Last Post: November 8th 2011, 08:42 PM
  2. Trigonometric Identities
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: November 4th 2011, 06:06 AM
  3. Trigonometric identities.
    Posted in the Trigonometry Forum
    Replies: 14
    Last Post: November 5th 2010, 08:43 AM
  4. trigonometric identities
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: November 26th 2008, 03:03 PM
  5. trigonometric identities
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: May 19th 2008, 09:25 PM

Search Tags


/mathhelpforum @mathhelpforum