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Math Help - SolidMensuration

  1. #1
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    SolidMensuration

    Questions from Kern and Bland pp8 #'s 17,19,21




    19. The base of an isosceles triangle is 16 in. and the altitude is 15 in. Find the radius of the inscribed circle.





    PLEASE HELP THANKS!! ^__^


    in #17 about the race track i can't read clearly the value of SC = ..... maybe perhaps it is too old copy.. ^^
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  2. #2
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    What are you asking for? Full solutions? How far did you get?

    On the 1/4 mile track: did you calculate that the semi-circles each have length of 345,
    calculated this way : (5280/4 - 630) / 2 ?

    Did you do some "searching", like Googling "inscribed circle of isosceles triangle" ?
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  3. #3
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    Quote Originally Posted by Wilmer View Post
    What are you asking for? Full solutions? How far did you get?

    On the 1/4 mile track: did you calculate that the semi-circles each have length of 345,
    calculated this way : (5280/4 - 630) / 2 ?

    Did you do some "searching", like Googling "inscribed circle of isosceles triangle" ?

    #17..Where did you get this formula?? And how? I can't still figure it out.But I know that the race track which is equal to 1mile should be divide in order to get a quarter mile..

    #19..I did some research and this is what i found out..

    r = 2*(area of triangle) / (a+b+c)
    = 2 * [0.5 * 4 * √(3^2 - (4/2)^2)] / (3+3+4)
    = 2 * 2√5 / 10
    = 2 / √5

    Now my questions is..how did it come up with that kind of formula in "r".??

    #21..It's hard.. I tried to use trigonometric functions.. T_T
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  4. #4
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    Quote Originally Posted by cutiemike1 View Post
    ....But I know that the race track which is equal to 1mile...
    WHERE did you get 1 mile? Problem clearly states 1/4 mile.
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  5. #5
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    oh yeah! i'm sorry...
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