Results 1 to 2 of 2

Math Help - Trig functions

  1. #1
    Member
    Joined
    Oct 2008
    Posts
    221

    Post Trig functions

    1) Find the exact measures of sin2x, cos2x, and tan2x using the double angle formulas, that sinx = -12/13. Show all work.

    2) Find the exact value of the trig function given that sinx = 12/13 and cosy = -4/5 and you are in Quadrant 2. Show all work.

    3) Find all solutions of the equation cosx + sin2x = 0 in the interval [0, 2π). For this one, I changed sin2x to 2sinxcosx, then factored out a cosx, for it to be cosx(1 + 2sinx), but am unsure where to go from there.

    Any help is appreciated!
    Thanks.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    12,110
    Thanks
    982
    Quote Originally Posted by live_laugh_luv27 View Post
    1) Find the exact measures of sin2x, cos2x, and tan2x using the double angle formulas, that sinx = -12/13. Show all work.

    2) Find the exact value of the trig function given that sinx = 12/13 and cosy = -4/5 and you are in Quadrant 2. Show all work.

    3) Find all solutions of the equation cosx + sin2x = 0 in the interval [0, 2π). For this one, I changed sin2x to 2sinxcosx, then factored out a cosx, for it to be cosx(1 + 2sinx), but am unsure where to go from there.

    Any help is appreciated!
    Thanks.
    1. to use the double angle formulae, you need the value of \cos{x} and the quadrant that x resides (III or IV, since \sin{x} < 0). use the Pythagorean identity or a reference triangle to find the value of \cos{x}

    2. "Find the exact value of the trig function ... "

    what trig function? Is there more information to this question?

    3. \cos{x}(1 + 2\sin{x}) = 0

    set each factor equal to zero ...

    \cos{x} = 0 , 1 + 2\sin{x} = 0

    solutions for x will be angles from the unit circle ...

    for the first factor, \cos{x} = 0 at x = \frac{\pi}{2} and \frac{3\pi}{2}

    you solve for the second factor.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Trig Equation with varied trig functions
    Posted in the Trigonometry Forum
    Replies: 12
    Last Post: April 12th 2010, 11:31 AM
  2. Replies: 2
    Last Post: September 24th 2009, 10:43 PM
  3. Inverse Trig Functions and Advance Trig
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: September 24th 2008, 04:13 PM
  4. Trig Equations with Multiple Trig Functions cont.
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: April 7th 2008, 06:50 PM
  5. Trig Equations with Multiple Trig Functions help
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: April 6th 2008, 06:48 PM

Search Tags


/mathhelpforum @mathhelpforum