Results 1 to 3 of 3

Math Help - Sine Rule q

  1. #1
    Junior Member
    Joined
    Dec 2009
    Posts
    61

    Sine Rule q

    If A = 18degrees, b - a =2, ab =4, using the usual notation fora triangle, use the sine rule to find B.
    Help I keep getting this q wrong in my book it says the answer is 53.85, but i keep getting like 53.999.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    Quote Originally Posted by Detanon View Post
    If A = 18degrees, b - a =2, ab =4, using the usual notation fora triangle, use the sine rule to find B.
    Help I keep getting this q wrong in my book it says the answer is 53.85, but i keep getting like 53.999.
    Solve the simultaneous equations for a and b

    a = -1+ \sqrt{5} : b = 1+\sqrt{5}

    \frac{sinA}{a} = \frac{sinB}{b}


    B = arcsin \left(\frac{b}{a}sinA\right) = arcsin \left(\frac{1+\sqrt5}{1-\sqrt5}sin(18)\right) =

    How odd, I get -54 exactly
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Jul 2009
    Posts
    192
    Thanks
    4
    i get exactly 54.

    but thats without rounding. and the book is way off.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Sine rule...
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: September 22nd 2009, 03:46 PM
  2. Sine rule!
    Posted in the Geometry Forum
    Replies: 2
    Last Post: May 13th 2009, 01:40 PM
  3. sine rule
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: March 13th 2009, 09:12 PM
  4. The Sine Rule
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: March 31st 2008, 09:03 PM
  5. sine rule
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: November 19th 2006, 05:30 AM

Search Tags


/mathhelpforum @mathhelpforum