Results 1 to 5 of 5

Math Help - I'm having trouble getting the right answer to this ...

  1. #1
    Newbie
    Joined
    Jul 2011
    Posts
    3

    I'm having trouble getting the right answer to this ...

    For the sake of interest only ..
    I am trying to build an applicatin that will predict the position of the sun in the sky (horizontal and vertical angle) for any given date and geographical location for any of the planets in our solar system.

    So far so good, but ...
    The following sum, I am reliably informed, should equate to: 1.9142

    1.9148 * sin(87.1807) + 0.0200 * sin(2 * 87.1807) + 0.0003 * sin(3 * 87.1807)

    I am getting: -1.3721

    I'm probably making a school boy error.
    Any help would be welcome.

    Regards

    Ben Stevens
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    11,569
    Thanks
    1428

    Re: I'm having trouble getting the right answer to this ...

    For starters, sine is negative in the third quadrant, so the third term will be negative. Question is, is it greater in magnitude than the other two terms?

    Also, have you made sure that your calculator is in degree mode?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member kalyanram's Avatar
    Joined
    Jun 2008
    From
    Bangalore, India
    Posts
    143
    Thanks
    14

    Re: I'm having trouble getting the right answer to this ...

    Hi Ben

    sin(87.1807) = 0.99878962570209612689563534191579
    sin(2*87.1807) = 0.098253359368085150710143684506237
    sin(3*87.1807) = -0.98912420429733530840698149621533
    Substituting in the equation we have
    1.9148 * sin(87.1807) + 0.0200 * sin(2 * 87.1807) + 0.0003 * sin(3 * 87.1807)= 1.9141507052204461662014433319416
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Jul 2011
    Posts
    3

    Re: I'm having trouble getting the right answer to this ...

    Many thanks Kalyanram ..
    I now know that I'm wrong at least.

    I am working with Visual Basic in .Net
    I get the following componet parts to the equation.. which would appear to be wrong.

    ?Math.Sin(M)
    -0.7060425903472024
    ?Math.Sin(2 * M)
    -0.99999547679626677
    ?Math.Sin(3 * M)
    -0.71028974892604

    I should think I need to be looking at how VB calculates the SIN of a given angle.

    Once again.
    Many thanks
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Jul 2011
    Posts
    3

    Re: I'm having trouble getting the right answer to this ...

    Thanks Prove It.
    I haven't checked, but I will.
    As I have said in another reply, I am working in VB .Net.

    Assuming kalyanram is correct, the vb .Net SIN function is returning an unexpected result.
    I'm probably not using it correctly.

    Once again.
    Many thanks
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 5
    Last Post: March 3rd 2013, 07:17 PM
  2. Converting my answer into the books answer
    Posted in the Algebra Forum
    Replies: 6
    Last Post: March 10th 2011, 02:06 PM
  3. Replies: 1
    Last Post: October 4th 2010, 04:46 PM
  4. Replies: 3
    Last Post: April 6th 2008, 03:18 PM

/mathhelpforum @mathhelpforum