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stupidinmath

  • 11 months ago

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  1. ganeshie8
    • 11 months ago
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    you have two arcs of radius 10

  2. ganeshie8
    • 11 months ago
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    each arc is measuring exactly 1/4th of circle (why ?)

  3. ganeshie8
    • 11 months ago
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    so you can calculate the perimeter of shaded region ?

  4. stupidinmath
    • 11 months ago
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    so.. if i get the arc measures.. i'll just add both then i can already have the perimeter?

  5. Andras
    • 11 months ago
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    Do you know what is the perimeter of a full circle? If you do you can find the shaded one. As that is twice the quarter of a circle. Thus 2*1/4=1/2 The perimeter is half of the full circle. (with radius=10)

  6. stupidinmath
    • 11 months ago
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    my answer is.. P=900, is it correct?

  7. Andras
    • 11 months ago
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    Seems wrong. \[\pi \] Is missing for sure.

  8. Andras
    • 11 months ago
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    What is the perimeter of a circle with radius=r?

  9. stupidinmath
    • 11 months ago
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    15.71 ?

  10. stupidinmath
    • 11 months ago
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    62.83

  11. Andras
    • 11 months ago
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    Do not try to jump steps. One at a time, otherwise you will make too many mistakes. So we will start with a circle of any radius=r. This circle has perimeter: \[P=2\pi r \] Is this clear?

  12. stupidinmath
    • 11 months ago
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    yep, perimeter's 62.83 approximately

  13. Andras
    • 11 months ago
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    If r=10 as in this question. Now next step, first look at one arc of the graph. (half the perimeter asked) What fraction is this arc of the full circle?

  14. stupidinmath
    • 11 months ago
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    1/4 of the circle

  15. Andras
    • 11 months ago
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    Correct, thus one arc has perimeter: \[\frac{ 1 }{ 4 } 2\pi r \]

  16. Andras
    • 11 months ago
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    We need two arcs, so need to multiply the above equation by 2. \[2*\frac{ 1 }{ 4 } 2\pi r =\pi r\]

  17. Andras
    • 11 months ago
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    \[solution: P=10\pi \]

  18. stupidinmath
    • 11 months ago
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    15.71.. so.. 31.42 :)

  19. stupidinmath
    • 11 months ago
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    did i get it right?

  20. Andras
    • 11 months ago
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    Yes but I am 100% confident that your maths teacher will not like the solution written as 31.42, as it is not precise. The solution is \[10 \pi \]

  21. stupidinmath
    • 11 months ago
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    Hahah, yeah maybe. Alright. Got that. Thank you sooo much:)

  22. Kainui
    • 11 months ago
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    @Andras Don't be so sure. Often times in courses like this the teacher prefers that you assume pi=3.14, which is probably exactly what his teacher expects since he's already doing it this way.

  23. Andras
    • 11 months ago
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    You might be right but that hurts my soul :(

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