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Homework Help: HELP optimization derivative of trig functions, grade 11 math,give it a try please !

  1. Jan 9, 2010 #1
    1. The problem statement, all variables and given/known data
    there's a picture of the question... from my text book
    http://photos-h.ak.fbcdn.net/hphotos..._1385551_n.jpg [Broken]
    thers a diagram image of the problem too to help understand

    2. Relevant equations

    well its a word problem,
    i used cosine rule at beginining and then pythagoras...i dont know what to do next but i think you calculare the area and then derivative. but i dont know how (whats the equation for the area)

    3. The attempt at a solution
    well i used the cosine rule for triangle BCO
    BC^2 = 10^2 + 10^2 - 2x10x10 cosθ
    BC = √(200-200cosθ)
    XY = BC


    BY^2 = BX^2 + XY^2 =
    400 = BX^2 + (200-200cosθ)
    BX^2 = 200 + 200cosθ
    BX = √(200+200cosθ)

    now what do i do?


    reply asap ! :P thankss !!
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Jan 9, 2010 #2
    Re: HELP optimization derivative of trig functions, grade 11 math,give it a try pleas

    I can't get access to that web site... so you better go with another uploading site like tinypic.com or somewhere else!

    AB
     
    Last edited by a moderator: May 4, 2017
  4. Jan 9, 2010 #3
    Re: HELP optimization derivative of trig functions, grade 11 math,give it a try pleas

    oh sorry ! here you go
    i hope this way works

    http://es.tinypic.com/r/2exa4yb/6

    and heres the old link again, fixed it

    http://photos-h.ak.fbcdn.net/hphotos-ak-snc3/hs145.snc3/17245_418921415214_614755214_10740817_1385551_n.jpg [Broken]
     
    Last edited by a moderator: May 4, 2017
  5. Jan 9, 2010 #4
    Re: HELP optimization derivative of trig functions, grade 11 math,give it a try pleas

    I've given all hints needed for the complete answer in the following picture:

    http://www.freeimagehosting.net/uploads/th.3b37fcda70.jpg

    As for the second question, the only hint is that take the first derivative of the area with respect to theta and then equate the resulting equation with zero. The theta from the new equation with an accuracy of 1/10 of a degree will be your desirable answer.

    AB
     
    Last edited by a moderator: May 4, 2017
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