Results 1 to 6 of 6

Math Help - simplify

  1. #1
    Junior Member
    Joined
    Jul 2009
    Posts
    35

    simplify

    5 [cosθ cos 53.13 deg - sinθ sin 53.13 deg] sinθ
    =3cosθ -4sinθ

    Can someone tell me how it arrive as 3cosθ -4sinθ ? Thanks ^^
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member
    Joined
    Aug 2009
    From
    Mumbai
    Posts
    83
    Because Cos53.13 = 3/5 and sin53.13=4/5 (approximately.)
    Follow Math Help Forum on Facebook and Google+

  3. #3
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    Quote Originally Posted by jasonlewiz View Post
    5 [cosθ cos 53.13 deg - sinθ sin 53.13 deg] sinθ
    =3cosθ -4sinθ

    Can someone tell me how it arrive as 3cosθ -4sinθ ? Thanks ^^
    cos(\alpha)cos(\beta) - sin(\alpha)sin(\beta) = cos(\alpha + \beta)
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,621
    Thanks
    426
    Quote Originally Posted by jasonlewiz View Post
    5 [cosθ cos 53.13 deg - sinθ sin 53.13 deg] sinθ
    =3cosθ -4sinθ

    Can someone tell me how it arrive as 3cosθ -4sinθ ? Thanks ^^
    \cos(53.13^\circ) \approx \frac{3}{5}

    \sin(53.13^\circ) \approx \frac{4}{5}

    left side of the equation ...

    5\left[\cos{\theta} \cdot \frac{3}{5} - \sin{\theta} \cdot \frac{4}{5}\right]
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Member
    Joined
    Aug 2009
    From
    Mumbai
    Posts
    83
    Ya the same.
    But I think there is a typo in the actual question.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,621
    Thanks
    426
    Quote Originally Posted by bandedkrait View Post
    Ya the same.
    But I think there is a typo in the actual question.
    5 [cosθ cos 53.13 deg - sinθ sin 53.13 deg] sinθ
    =3cosθ -4sinθ
    yes ... the extra sinθ
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. simplify #2
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: September 21st 2009, 02:37 PM
  2. Please simplify
    Posted in the Trigonometry Forum
    Replies: 4
    Last Post: April 27th 2009, 04:32 AM
  3. Can you simplify this further?
    Posted in the Algebra Forum
    Replies: 4
    Last Post: April 23rd 2009, 06:45 AM
  4. Simplify
    Posted in the Algebra Forum
    Replies: 2
    Last Post: April 12th 2009, 05:06 AM

Search Tags


/mathhelpforum @mathhelpforum