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zuha

  • one year ago

A circle has an area of approximately 78.5 square units. If the center of the circle is at (2,4). Which of the following points is on the circle?

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  1. Zuha
    • one year ago
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    (-6, 4) (2, -1) (-4, -4) (2, -9)

  2. Nnesha
    • one year ago
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    do you know the standard form equation of the circle ?

  3. Zuha
    • one year ago
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    Do you mean the distance?

  4. Nnesha
    • one year ago
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    yes same equation for both

  5. Zuha
    • one year ago
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    Yyeah, I can't understand how to calculate that, I do know the d formula tho ;v;

  6. Nnesha
    • one year ago
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    well the standard form equation of the circle is \[\huge\rm (x-h)^2 +(y-k)=r^2\] where (h,k) is the center and r = radius

  7. Nnesha
    • one year ago
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    use the formula area of a circle \[\huge\rm A= \pi r^2\] to find r (radius )

  8. Zuha
    • one year ago
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    is (y-k) also supposed to be ^2? So is h=2 and k=4??

  9. Nnesha
    • one year ago
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    yes right forgot sorry about that \[\huge\rm (x-h)^2 +(y-k)^2=r^2\]

  10. Nnesha
    • one year ago
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    yes right h=2 k =4

  11. Zuha
    • one year ago
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    And I should just try each of the options until one of them is 78.5...?

  12. Zuha
    • one year ago
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    @Nnesha ?

  13. Nnesha
    • one year ago
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    thanks for tag i was afk alright first you need to find the radius

  14. Nnesha
    • one year ago
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    the given is 78.5 area so substitute a for 78.5 and then solve for r

  15. Zuha
    • one year ago
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    a?

  16. Nnesha
    • one year ago
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    what do you mean ?

  17. Nnesha
    • one year ago
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    use the formula area of a circle \[\huge\rm A= \pi r^2\] to find radius

  18. Zuha
    • one year ago
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    Oohhhh 78.5=pir^2 Umm, I assume I divide pi from both sides then?

  19. Nnesha
    • one year ago
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    yes right

  20. Zuha
    • one year ago
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    25 o.o

  21. Zuha
    • one year ago
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    So I do 3.14*25^2?

  22. Nnesha
    • one year ago
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    yes r^2 equal 25 yes right forgot sorry about that \[\huge\rm (x-2)^2 +(y-4)^2=25\] now you can substitute (x,y) for each order pair if you get equal sides then that order pair would be the answer

  23. Nnesha
    • one year ago
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    no we need r^2 which is 25 you can check your work 3.14*25^2 iif its equal 78.5 then 25 is correct

  24. Zuha
    • one year ago
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    It isn't equal to 78.5 .-.

  25. Nnesha
    • one year ago
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    r^2 =25 not r= so dont' take square of 25

  26. Nnesha
    • one year ago
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    \[\huge\rm \frac{ 78.5 }{ 5 }=r^2 ~~~~----> 25=r^2\] to find r you should take square root but we need r^2 for the equation

  27. Zuha
    • one year ago
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    Ooh Okay, then yeah it's right--so then I just try each of the answers in the slots for x and y until I get the right one?

  28. Nnesha
    • one year ago
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    yep!

  29. Zuha
    • one year ago
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    Oh okay! I already know the correct answer which is (2,-1) and I tested it and it's right! Thanks so much!! :)

  30. Nnesha
    • one year ago
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    np :=)goood work!

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