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Math Help - math questions

  1. #1
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    math questions

    2.In triangle ABC, B=65 degrees, b=2 and c=12. How many triangles are possible?

    3. Find sin2942' to four decimal places_

    4. Find sec178'49" to four decimal places

    5.Which of the following statements would give the largest value of theta if theta was less then 90?
    a)7sinTHETA=4
    b)5cosTHETA=2
    c)4tanTHETA=6
    d)8cscTHETA=10
    ------
    I tried to put number 3 and 4 into a caluculator but the answers were wrong.

    I converted (5) to sintheta=4/7 etc, costheta=2/5.. but I don't know how to finish from there

    I am completely lost at number 2
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  2. #2
    Newbie
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    Fairfield, Ca
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    2. one?... ABC ... are you sure thats the whole question?

    5. plug in arcsin4/7 (arccos2/5, etc...)into yer calculator...
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  3. #3
    zeg
    zeg is offline
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    Portland, OR
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    suggestion

    #3 & #4 ~ I would suggest converting degrees, minutes, seconds into decimal degrees. For example 20^{\circ}30' would be 20.5^{\circ}. Remember, there are 60 minutes in a degree and 60 seconds in a minute (arcminutes and arcseconds, not time mins. and sec.).
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  4. #4
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    Lexington, MA (USA)
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    Hello, ceroseven!

    2.In \Delta ABC\!:\;\;B=65^o,\;\;b=2,\;\;c=12
    How many triangles are possible?
    Did you make a sketch?

    If such a triangle were possible, it might look like this:
    Code:
                  C
                  *
                 / \
                /   \
               /     \
              /       \ 2
             /         \
            /           \
           / 65         \
        B * - - - - - - - * A
                  12


    Law of Sines: . \frac{\sin C}{c} \:=\:\frac{\sin B}{b}

    So we have: . \frac{\sin C}{12} \:=\:\frac{\sin 65^o}{2} \quad\Rightarrow\quad \sin C \:=\:\frac{12\sin65^o}{2} \:\approx\:5.44


    Then: . C \:=\:\arcsin(5.44) \:=\:??? . . . which does not exist.


    Therefore, it is no triangle.

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