Results 1 to 6 of 6

Math Help - Finding intersection of trig and non trig function

  1. #1
    Junior Member
    Joined
    Feb 2011
    Posts
    28

    Finding intersection of trig and non trig function

    Hello

    I'm having trouble figuring out the steps needed to solve the intersection between

    f(x) = Cos (x)
    f(x) = 1 - (2x/Pi)

    I don't need the answer, only the steps used to solve such a problem. Thanks
    Last edited by skyd171; February 19th 2011 at 06:22 PM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by skyd171 View Post
    Hello

    I'm having trouble figuring out the steps needed to solve the intersection between

    f(x) = Cos (x)
    f(x) = 1 - (2x/Pi)

    I don't need the answer, only the steps used to solve such a problem. Thanks
    By inspection, x = 0 and x = pi are clearly solutions. There is one more solution but it cannot be found using algebra. In general equations involving such 'mixed functions' cannot be solved exactly using algebra, only approximate solutions using a CAS or numerical procedure can be found.
    Last edited by mr fantastic; February 19th 2011 at 06:34 PM. Reason: Added comment about one other solution.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Feb 2011
    Posts
    28

    Post

    Shame, I've spent about 4 hours trying to solve it with algebra only to find that out. This professor is a real piece of work.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by skyd171 View Post
    Shame, I've spent about 4 hours trying to solve it with algebra only to find that out. This professor is a real piece of work.
    My previous post contains an error. The other solution is, again by inspection, x = pi/2.

    If you are required to solve exactly equations like this without using technology, the solutions are generally designed to be so simple and obvious that they can be easily seen 'by inspection'. In fact, drawing accurate graphs would have put you on the right track and probably saved you 3 hours and 55 minutes of your time.

    I have no problem with what your professor has asked you to do.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Feb 2011
    Posts
    28
    Yes, I used guess and check with graphs to find this solution. However I had been searching the web for hours for a proper algebraic way to find those roots and alternatively trying to find them numerically on my own. But it is just as informative to know that there is none.

    This was only a small taste of my prof. The next problem (which I will not even bother to offend anyone here with) is
    finding the area between 7 functions, the graphs of which look like a spider web. He is a swell guy.

    thanks for the help
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by skyd171 View Post
    [snip] The next problem (which I will not even bother to offend anyone here with) is
    finding the area between 7 functions, the graphs of which look like a spider web. He is a swell guy.

    thanks for the help
    Use of symmetry will most likely simplify the calculations.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Finding trig intersection point
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: March 4th 2011, 03:53 PM
  2. Finding trig functions with one known function
    Posted in the Pre-Calculus Forum
    Replies: 5
    Last Post: September 9th 2009, 03:53 PM
  3. Finding the equation of trig function
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: May 9th 2009, 12:23 PM
  4. Trig Function Intersection
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: May 8th 2009, 11:27 AM
  5. Finding a trig function given the value of another
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: April 23rd 2009, 10:30 PM

Search Tags


/mathhelpforum @mathhelpforum