Results 1 to 2 of 2

Math Help - solutions for tan and sin

  1. #1
    Junior Member
    Joined
    Nov 2006
    Posts
    62

    solutions for tan and sin

    I am working on a few problems for a test tommorrow and I would like to know if Tan(x/3)= 3.8 and 2sin3x=cosx can be solved by putting tan(x/3) in y1 and 3.8 in y2 or is there a better way? The study sheet tells me to find all solutions to 3 decimals. I would appreciate any method you could provide.
    Thank you!
    Keith Stevens
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Forum Admin topsquark's Avatar
    Joined
    Jan 2006
    From
    Wellsville, NY
    Posts
    9,901
    Thanks
    329
    Awards
    1
    Quote Originally Posted by kcsteven View Post
    I am working on a few problems for a test tommorrow and I would like to know if Tan(x/3)= 3.8 and 2sin3x=cosx can be solved by putting tan(x/3) in y1 and 3.8 in y2 or is there a better way? The study sheet tells me to find all solutions to 3 decimals. I would appreciate any method you could provide.
    Thank you!
    Keith Stevens
    I'm not clear on what your question is. You have two equations to solve for x, but your reference to y1 and y2 sounds like you are graphing them together somehow?

    The only way I know how to solve tan(x/3) = 3.8 would be to use a calculator to get a numerical estimate: x = 3 \cdot tan^{-1}(3.8). Another way (perhaps this is what you were trying to get at) would be to graph the two functions:
    y = tan(x/3)
    y = 3.8
    simultaneously and find the points of intersection on the graphics screen.

    An alternate way of getting a "graphical" solution would be to graph
    y = tan(x/3) - 3.8 and use the "zeros" function on your calculator.

    You can sort of solve 2sin(3x)=cos(x) analytically, that is to say that you can do some work with the equation before you approximate the solution. (Expand the sin(3x) and write everything in terms of just sin(x) and this will give you a 6th degree polynomial in sin(x). Then numerically approximate the solution.) Probably the best way is to graph:
    y = 2sin(3x)
    y = cos(x)
    and look for intersection points.

    -Dan
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: October 4th 2011, 08:21 PM
  2. solutions
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: November 11th 2010, 05:07 AM
  3. Replies: 6
    Last Post: July 26th 2010, 11:45 AM
  4. help with ODE. *i got no solutions
    Posted in the Differential Equations Forum
    Replies: 1
    Last Post: October 10th 2009, 09:12 AM
  5. Solutions to ODE y'(t) = t^2 +y(t)^2
    Posted in the Differential Equations Forum
    Replies: 1
    Last Post: January 18th 2009, 12:44 AM

Search Tags


/mathhelpforum @mathhelpforum