Results 1 to 4 of 4

Math Help - Linear Trig Functions help please!

  1. #1
    Newbie
    Joined
    Dec 2007
    Posts
    3

    Linear Trig Functions help please!

    hey! can anybody please help me solve this question please!
    2Cos(x/2)=square root two
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Newbie
    Joined
    Dec 2007
    Posts
    3
    or this question:
    5cos3x=-3
    thank-you!please reply!
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Super Member

    Joined
    May 2006
    From
    Lexington, MA (USA)
    Posts
    11,740
    Thanks
    645
    Hello, Jane!

    2\cos\left(\frac{x}{2}\right)\;=\;\sqrt{2}

    Divide by 2: . \cos\left(\frac{x}{2}\right) \:=\:\frac{\sqrt{2}}{2}

    Now what angle has a cosine of \frac{\sqrt{2}}{2} ?
    . . That's right . . . \pm\frac{\pi}{4} + 2\pi n

    So we have: . \frac{x}{2} \:=\:\frac{\pi}{4} + 2\pi n

    Therefore: . \boxed{x \:=\:\frac{\pi}{2} + 4\pi n}



    5\cos(3x)\:=\:-3
    We have: . \cos(3x) \:=\:\text{-}\frac{3}{5}

    Then: . 3x \:=\:\cos^{\text{-}1}\left(\text{-}\frac{3}{5}\right)

    Therefore: . \boxed{x \;=\;\frac{1}{3}\cos^{\text{-}1}\left(\text{-}\frac{3}{5}\right)}

    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Dec 2007
    Posts
    3
    thanks a lot!
    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, 10:31 AM
  2. Replies: 2
    Last Post: September 24th 2009, 09:43 PM
  3. Inverse Trig Functions and Advance Trig
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: September 24th 2008, 03:13 PM
  4. Trig Equations with Multiple Trig Functions cont.
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: April 7th 2008, 05:50 PM
  5. Trig Equations with Multiple Trig Functions
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: April 6th 2008, 03:48 PM

Search Tags


/mathhelpforum @mathhelpforum