Results 1 to 3 of 3

Math Help - Solving trig equations- Is this right?

  1. #1
    Newbie
    Joined
    Feb 2009
    Posts
    9

    Solving trig equations- Is this right?

    sin(2A)=6sin(A)

    2sinAcosA-6sinA=0

    2sinA(cosA-3) = 0

    sinA= 2 or cosA=3

    So, are there no solutions?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Rhymes with Orange Chris L T521's Avatar
    Joined
    May 2008
    From
    Chicago, IL
    Posts
    2,844
    Thanks
    3
    Quote Originally Posted by coasterguy View Post
    sin(2A)=6sin(A)

    2sinAcosA-6sinA=0

    2sinA(cosA-3) = 0

    sinA= 2 or cosA=3

    So, are there no solutions?
    From the line 2\sin A\left(\cos A-3\right)=0, you should get the two equations 2\sin A=0 or \cos A-3=0. If A\in\mathbb{R}, the second one is never true (If A\in\mathbb{C}, then it would be a different story). The first one has a solution, since 2\sin A=0\implies \sin A=0 which is true when A=k\pi, where k\in\mathbb{Z} ( \mathbb{Z} is the set of integers).

    Does this make sense?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Feb 2009
    Posts
    6

    solve this equation

    let z = { -1,-2,-3,....,0.1.2.3....}= the set of integre numbers
    Attached Thumbnails Attached Thumbnails Solving trig equations- Is this right?-po18.jpg  
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Solving Trig. Equations
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: May 3rd 2010, 10:14 PM
  2. Solving Trig Equations Help
    Posted in the Trigonometry Forum
    Replies: 5
    Last Post: March 14th 2010, 08:47 PM
  3. 3 solving trig equations
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: November 25th 2008, 07:09 PM
  4. solving trig equations
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: June 2nd 2008, 08:48 PM
  5. solving trig equations
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: November 14th 2007, 02:29 PM

Search Tags


/mathhelpforum @mathhelpforum