Results 1 to 5 of 5

Math Help - Help solve trig func equation and identity

  1. #1
    Newbie
    Joined
    Dec 2009
    Posts
    2

    Help solve trig func equation and identity

    Help solve trig func equation and identity


    Hello! I have problems with these two questions!

    1) Solve for 0<= x <= 2pi
    --> cosx (1-2sinx) = 0

    (Looking for rad. answers in the range)

    ------------------------------------------
    2) Prove this identity:
    --> cosx/(1-sinx) - secx = tanx

    (LS = RS)

    Would be great to get some steps!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,700
    Thanks
    454
    Quote Originally Posted by Genuine View Post
    Help solve trig func equation and identity


    Hello! I have problems with these two questions!

    1) Solve for 0<= x <= 2pi
    --> cosx (1-2sinx) = 0

    set each factor equal to 0 ...

    cosx = 0 ... x = ?

    sinx = 1/2 ... x = ?

    you should know the solutions to these based on your knowledge of the unit circle.

    (Looking for rad. answers in the range)

    ------------------------------------------
    2) Prove this identity:
    --> cosx/(1-sinx) - secx = tanx

    [cosx/(1-sinx)]*[(1+sinx)/(1+sinx)] - secx =

    cosx(1+sinx)/(1-sin^2x) - secx =

    cosx(1+sinx)/cos^2x - secx =

    (1+sinx)/cosx - 1/cosx =

    finish ...



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

  3. #3
    Super Member bigwave's Avatar
    Joined
    Nov 2009
    From
    honolulu
    Posts
    580
    cosX = 0

    cos^{-1}\left(0\right) = \frac{\pi}{2} and \frac{3\pi}{2}
    --------------------------------------------------------------

    1 - 2sinX = 0

     <br />
2sinX = 1<br />

     <br />
SinX = \frac{1}{2}<br />

      <br />
sin^{-1}\left(\frac{1}{2}\right) = \frac{\pi}{6} and  \frac{5\pi}{3}
    Last edited by bigwave; December 8th 2009 at 04:43 PM. Reason: latex
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Dec 2009
    Posts
    2

    still puzzled with 1)

    Thank you very much for the fast response!
    I understand 2) [thanks skeeter!]
    What exactly do you mean "set each factor equal to 0 ..." ?
    Im probly just not familiar with the wording
    Follow Math Help Forum on Facebook and Google+

  5. #5
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,700
    Thanks
    454
    Quote Originally Posted by Genuine View Post
    Thank you very much for the fast response!
    I understand 2) [thanks skeeter!]
    What exactly do you mean "set each factor equal to 0 ..." ?
    Im probly just not familiar with the wording
    cosx(1-2sinx) = 0

    cosx is a factor , (1-2sinx) is a factor

    if two or more factors multiply to 0, then each factor has the possibility of equaling 0.

    cosx = 0

    1-2sinx = 0
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. trig identity equation
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: March 24th 2011, 06:44 AM
  2. trig equation and identity help.
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: March 31st 2010, 03:00 PM
  3. A Quick Trig Identity Problem That I Need To Solve
    Posted in the Advanced Applied Math Forum
    Replies: 8
    Last Post: March 29th 2010, 10:37 PM
  4. Prove an identity and solve an equation
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: November 19th 2009, 07:31 AM
  5. Trig Identity/Equation
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: February 2nd 2009, 11:12 AM

Search Tags


/mathhelpforum @mathhelpforum