Results 1 to 2 of 2

Math Help - Need some help with solving equations

  1. #1
    Junior Member
    Joined
    Sep 2007
    Posts
    55

    Need some help with solving equations

    I am having a lot of trouble with these questions.

    6. 5(sin 6t - 4cos 4t) = 0

    -----------------------------------------------------

    10. a) 3sin^2x - 8sinx - 3 = 0

    This one I kinda get, but I am having some trouble with it.

    The factors can be found like this right?

    so therefore ... 3sinx + 1 =0 and sinx - 3 =0

    For 3sinx+1=0, you move 1 over, so it becomes 3sinx = -1

    You then divide by 3 so it equals sinx = -1/3

    it then becomes x = sin^-1(-1/3) but that's as far as I know how to do it.

    -----------------------------------------------------


    I have the answers to these, I just need to know how you get each step to solve the answer.

    Also, I have a question concerning angles. For example, would -20 deg, be the same as 20 deg and how so?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member

    Joined
    May 2006
    From
    Lexington, MA (USA)
    Posts
    11,659
    Thanks
    600
    Hello, finalfantasy!

    10\;a)\;\;3\sin^2\!x - 8\sin x - 3 \:=\: 0

    The factors can be found like this, right? . (3\sin x + 1)(\sin x -3) \:=\:0 . . . . Right!

    So therefore: .[1] 3\sin x + 1 \:=\:0 .and .[2] \sin x - 3 \:=\:0 . . . . Yes!

    For [1]: . 3\sin x + 1\:=\:0, you move 1 over,
    . . so it becomes: . 3\sin x \: = \:-1
    . . You then divide by 3, so it equals: . \sin x \:= \:-\frac{1}{3}
    . . It then becomes: . x \:=\:\sin^{-1}\left(-\frac{1}{3}\right) . . . . Good!

    but that's as far as I know how to do it.

    Now do the same for [2]: . \sin x - 3 \:=\:0

    Move the -3 over: . \sin x \:=\:3

    And this equation has no solution.
    . . [ \sin x is always between -1 and +1.]


    Therefore, your answer is the only solution: . x \;=\;\sin^{-1}\left(-\frac{1}{3}\right)
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 6
    Last Post: November 30th 2011, 01:41 AM
  2. Solving two equations
    Posted in the Algebra Forum
    Replies: 7
    Last Post: November 21st 2011, 02:55 PM
  3. Solving equations
    Posted in the Algebra Forum
    Replies: 29
    Last Post: November 18th 2011, 06:05 AM
  4. Solving these equations...
    Posted in the Differential Equations Forum
    Replies: 1
    Last Post: April 27th 2009, 05:06 AM
  5. solving equations
    Posted in the Algebra Forum
    Replies: 3
    Last Post: May 16th 2006, 03:58 PM

Search Tags


/mathhelpforum @mathhelpforum