Results 1 to 6 of 6

Math Help - Trig question.. finding an exact expression.

  1. #1
    Member
    Joined
    Nov 2009
    Posts
    171

    Trig question.. finding an exact expression.

    A cruise ship sailed north for 50 km. Then, the captain turned the ship eastward through an angle of pi/6 and sailed an additional 50 km. Without using a calculator, determine an exact expression for the direct distance from the start to the finish of the cruise.

    So I started by trying to draw the problem:



    Did I even draw it right? And to finish it off how do I determine an exact expression? Please show all work done to get to the expression.

    Answer:
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Sep 2008
    From
    West Malaysia
    Posts
    1,261
    Quote Originally Posted by kmjt View Post
    A cruise ship sailed north for 50 km. Then, the captain turned the ship eastward through an angle of pi/6 and sailed an additional 50 km. Without using a calculator, determine an exact expression for the direct distance from the start to the finish of the cruise.

    So I started by trying to draw the problem:



    Did I even draw it right? And to finish it off how do I determine an exact expression? Please show all work done to get to the expression.

    Answer:
    HI

    you can use the cosine rule ,

    x^2=50^2+50^2-2(50)(50)\cos 30
    Attached Thumbnails Attached Thumbnails Trig question.. finding an exact expression.-trigo-sin.bmp  
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Nov 2009
    Posts
    171
    So I did the cosine rule as you mentioned:

    a^2 = b^2 + c^2 -2bc(cos30)

    a^2 = 50^2 + 50^2 - 2(50)(50)cos30

    a^2 = 2500 + 2500 - 5000 (0.866)

    a^2 = 2500 + 2500 - 4330.127

    a^2 = 669.873

    a = 25.88190488

    I'm confused as to how doing that would help me determine an exact expression for the direct distance from the start to the finish of the cruise. I have no clue where the expression is coming from, please help. Once again the expression for the direct distance from the start to finish of the cruise is:



    I have no clue where thats coming from
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Dec 2009
    Posts
    2
    I'm also quite confused about the wording of the question and what the diagram should look like. P.S. When you used the cosine law it is not same as the rounded answer from the back of the text. The rounded answer should be approx 96.93 not 25.88. Also my class has not been taught to use the cosine law yet so I'm pretty sure you're not supposed to use it. If you are using Advanced Functions 12 by McGraw-Hill Ryerson.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Dec 2009
    Posts
    2
    This is basically what my diagram looked like. I do believe I was able to get the right answer. Sorry about the bad diagram.Trig question.. finding an exact expression.-untitledb.jpg
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Member
    Joined
    Nov 2009
    Posts
    171
    Yup your diagram is exactly correct. I figured it it yesterday and I also got 96.93
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Finding Exact Solutions Trig Equations
    Posted in the Trigonometry Forum
    Replies: 11
    Last Post: December 11th 2011, 04:42 PM
  2. Finding an exact expression for tan(pi/12)
    Posted in the Pre-Calculus Forum
    Replies: 5
    Last Post: August 25th 2010, 08:19 AM
  3. Finding the trig expression
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: May 12th 2010, 12:16 AM
  4. Finding Exact value of expression Analytical Trig
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: March 11th 2009, 05:07 PM
  5. Replies: 2
    Last Post: July 4th 2008, 12:38 PM

Search Tags


/mathhelpforum @mathhelpforum