Results 1 to 3 of 3

Thread: Finding roots of 3 sin^3 (x) + 5 sin^2 (x) - 2 sin(x) = 0 on (-pi, pi)

  1. #1

    Lightbulb Finding roots of 3 sin^3 (x) + 5 sin^2 (x) - 2 sin(x) = 0 on (-pi, pi)

    how do i determine the roots of 3 sin (cubed) x+5sin (squared) x-2sinx=0 on a (-pi,+pi) scale!

  2. #2
    Elite Member mmm4444bot's Avatar
    Join Date
    Oct 2005
    Location
    Seattle
    Posts
    8,935
    What have you done, so far? Where are you stuck?

    I'd begin by factoring the left-hand side of the given equation.

    Please be sure to read the forum guidelines. Thanks.
    "English is the most ambiguous language in the world." ~ Yours Truly, 1969

  3. #3
    Elite Member stapel's Avatar
    Join Date
    Feb 2004
    Posts
    15,514

    Cool

    Quote Originally Posted by Gr12math View Post
    how do i determine the roots of 3 sin (cubed) x+5sin (squared) x-2sinx=0 on a (-pi,+pi) scale?
    I'm not sure what you mean by "on a (-pi, +pi) scale"...? Do you perhaps mean "on the interval from [tex]-\pi[/tex] to [tex]+\pi,[/tex], not including the endpoints"...? If so, please confirm. If not, please correct.

    As for how to find the roots of the equation, use the usual methods, like they gave you in class and in your book. For this particular equation:

    You first noted that this is a quadratic in sin(x). You factored and created the two resulting (but simpler) trig equations. Then, using what you've memorized for standard angle values, etc, you solved each of the simpler equations (at least on the first quadrant), and... then what?

    Please be complete. Thank you!

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •