Results 1 to 2 of 2

Math Help - Writing a Sin and Cos Function Equation

  1. #1
    Senior Member
    Joined
    Nov 2008
    Posts
    425

    Writing a Sin and Cos Function Equation

    A sine function has a max value of 7, min value of -1. Phase shift is 3pi/4 to the left. Period is pi/2

    Write an equation for the function and then graph the function..

    Ok, I did this question, and my equation was something like this:

    y=4sin(4(x+3pi/4))

    However, in the back of the book. The answer is y=4sin(4(x+3pi/4))+3

    The k value in the equation? I am not sure how to get this k value.

    How would I figure this out? Am I wrong or is it wrong in the back?

    thank you
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Nov 2008
    From
    France
    Posts
    1,458
    Hi

    Your answer is not correct because your minimum is -4 and your maximum is 4

    The mean value is (7+(-1))/2 = 3 = number to be added to sine

    The amplitude is max-mean = mean-min = 7 - 3 = 3 - (-1) = 4 = factor of sine

    The period is pi/2 therefore sine is applied to (4x + phi) because
    sin(4(x+pi/2) + phi) = sin(4x + 2pi + phi) = sin(4x + phi)

    The phase shift is phi = 3pi/4

    The function is therefore : 3 + 4sin(4x+3pi/4)
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Writing this Equation, need help!
    Posted in the Differential Geometry Forum
    Replies: 1
    Last Post: October 28th 2009, 04:46 PM
  2. Re -writing equation
    Posted in the Algebra Forum
    Replies: 1
    Last Post: October 26th 2009, 05:06 PM
  3. I need some help writing and equation please.
    Posted in the Algebra Forum
    Replies: 0
    Last Post: November 4th 2008, 02:54 PM
  4. Writing an Equation.
    Posted in the Algebra Forum
    Replies: 3
    Last Post: July 31st 2008, 06:38 AM
  5. Need help writing a function
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: October 27th 2006, 10:18 AM

Search Tags


/mathhelpforum @mathhelpforum