Results 1 to 6 of 6

Thread: Solving trig equations

  1. January 13th 2010, 01:06 PM #1
    Paymemoney
    Paymemoney is offline
    Super Member
    Joined
    Dec 2008
    Posts
    509

    Solving trig equations

    Hi
    I need help on solving some of the following equations:
    1) Solve cos^2(x)-cos(x)sin(x) for x = [0,2\pi].

    2)Solve sec(x)=2.5 in the interval [-\pi,\pi], giving the answers correct to two decimal places.


    P.S
    Follow Math Help Forum on Facebook and Google+
  2. January 13th 2010, 01:19 PM #2
    e^(i*pi)
    e^(i*pi) is offline
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    Quote Originally Posted by Paymemoney View Post
    Hi
    I need help on solving some of the following equations:
    1) Solve cos^2(x)-cos(x)sin(x) for x = [0,2\pi].

    2)Solve sec(x)=2.5 in the interval [-\pi,\pi], giving the answers correct to two decimal places.


    P.S
    1. What is this expression equal to? If it's equal to 0 then factor

    cos(x)(cos(x)-sin(x)) = 0

    cos(x)=0 or cos(x) = sin(x)


    2.Take the reciprocal of both sides

    cos(x) = \frac{2}{5}
    Follow Math Help Forum on Facebook and Google+
  3. January 13th 2010, 01:23 PM #3
    Paymemoney
    Paymemoney is offline
    Super Member
    Joined
    Dec 2008
    Posts
    509
    yeh the first question is equal to 0
    Follow Math Help Forum on Facebook and Google+
  4. January 13th 2010, 01:43 PM #4
    Paymemoney
    Paymemoney is offline
    Super Member
    Joined
    Dec 2008
    Posts
    509
    in question 2 I'm not sure if i have done it correct:
    sec(x)=\frac{1}{cos(x)}
    so \frac{1}{\frac{2}{5}}=2.5*\frac{2}{5}
    Follow Math Help Forum on Facebook and Google+
  5. January 14th 2010, 01:33 AM #5
    Paymemoney
    Paymemoney is offline
    Super Member
    Joined
    Dec 2008
    Posts
    509
    Quote Originally Posted by e^(i*pi) View Post
    1. What is this expression equal to? If it's equal to 0 then factor

    cos(x)(cos(x)-sin(x)) = 0

    cos(x)=0 or cos(x) = sin(x)
    i get two solutions for when cos(x)=0, which are \frac{\pi}{2} & \frac{3\pi}{2}.
    However how do you get the solutions for cos(x)=sin(x)
    Follow Math Help Forum on Facebook and Google+
  6. January 14th 2010, 01:38 AM #6
    Prove It
    Prove It is offline
    MHF Contributor Prove It's Avatar
    Joined
    Aug 2008
    Posts
    10,385
    Thanks
    756
    Quote Originally Posted by Paymemoney View Post
    i get two solutions for when cos(x)=0, which are \frac{\pi}{2} & \frac{3\pi}{2}.
    However how do you get the solutions for cos(x)=sin(x)
    Divide both sides by \cos{x}.


    So \tan{x} = 1.
    Follow Math Help Forum on Facebook and Google+
« Finding Max and Min | more solving trig questions »

Similar Math Help Forum Discussions

  1. Solving Trig Equations
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: December 28th 2010, 05:58 AM
  2. Solving trig equations
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: December 8th 2010, 05:06 PM
  3. Solving Trig Equations
    Posted in the Pre-Calculus Forum
    Replies: 5
    Last Post: February 25th 2009, 05:42 PM
  4. Solving trig Equations
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: May 5th 2008, 08:15 PM
  5. solving trig equations
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: February 7th 2007, 10:42 PM

Search Tags


/mathhelpforum @mathhelpforum