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Math Help - Trigo

  1. #1
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    Exclamation Trigo

    Two adjacent figures are represented by the isosceles trapezoid and the square.
    What is the difference in the area of these two figures ?
    EXAM TOMORROW ! and I dont understand
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    Last edited by cookiii; December 14th 2009 at 11:03 AM.
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  2. #2
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    Hello cookiii

    Welcome to Math Help Forum!
    Quote Originally Posted by cookiii View Post
    What is the measurement of the dimensions regular pentagon if one of the diagonals measures 10 cm? URGENTTT
    The interior angles of a regular pentagon are each 108^o. So two of the sides, together with a diagonal, form an isosceles triangle whose angles are 108^o, 36^o, 36^o. Draw the line of symmetry of this triangle, and you'll see that the length of the side of the pentagon is \frac{5}{\cos36^o}= 6.18 cm (to 2 d.p.)

    (If you need an exact answer, that's 5(\sqrt5-1) - which I'll explain if necessary.)

    Grandad
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  3. #3
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    Exclamation Trigoo

    thank you so muchh ! but i have another question because i have an exam tomorroww and i don't understand !
    Two adjacent figures are represented by the isosceles trapezoid and the square.
    What is the difference in the area of these two figures ?
    I made it on word document so it would be easier to answer
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  4. #4
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    Hello cookiii
    Quote Originally Posted by cookiii View Post
    thank you so muchh ! but i have another question because i have an exam tomorroww and i don't understand !
    Two adjacent figures are represented by the isosceles trapezoid and the square.
    What is the difference in the area of these two figures ?
    I made it on word document so it would be easier to answer
    Have a look at the attached diagram. You'll see that I've drawn in the height of the trapezium and marked the lengths of the sides of the right-angled triangle.

    Can you see why b = \tfrac12(33-21)=6 cm?

    Then a = \frac{6}{\cos 77^o} and h = 6\tan 77^o. (I'll leave you to work those out.)

    The area of the trapezium is \tfrac12(33 + 21)h=27h and the area of the square is a^2. I hope you can complete the question now.

    Grandad
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