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anonymous

  • 5 years ago

Find the surface area of the regular pentagonal pyramid. The apothem of the pentagon is 5.5cm and AB =10 cm. The edge base length at the bottom of the figure is 8cm. Round answers to the nearest tenth of a unit.

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  1. anonymous
    • 5 years ago
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    Surface area = 200 cm^2 can anyone see if this is right?

  2. amistre64
    • 5 years ago
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    apothem is the face height and not the pyramid height right?

  3. amistre64
    • 5 years ago
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    what is AB mean?

  4. amistre64
    • 5 years ago
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    prolly height of pyrimaid

  5. anonymous
    • 5 years ago
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    apothem is a line segment from the center of the polygon perpendicular to one of its sides.... AB is ... A is the tip of the pyramid... to the base.. an edge of a side

  6. anonymous
    • 5 years ago
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    B is on the bottom

  7. anonymous
    • 5 years ago
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    pentagonal 5 sides

  8. amistre64
    • 5 years ago
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  9. anonymous
    • 5 years ago
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    looks good

  10. amistre64
    • 5 years ago
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    8*5.5*5 is side areas, do we include the bottom as well?

  11. anonymous
    • 5 years ago
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    l^2 = (5.5)^2 + (4)^2 l = sqrt 5.5^2 + 4^2 sqrt yea... I think I did

  12. anonymous
    • 5 years ago
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    sqrt 30.25 + 16 sqrt 46.25 p = 6.8 1/2(40)(6.8) + 8^2 = 200

  13. amistre64
    • 5 years ago
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    sqrt((4^2) + (5.5^2)) = 6.80073525 doesnt = 10 sqrt((8^2) + (5.5^2)) = 9.7.... is close to 10 If the edge AB that runs slong the side is 10, that means the base is 16

  14. amistre64
    • 5 years ago
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  15. anonymous
    • 5 years ago
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    yes

  16. amistre64
    • 5 years ago
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    8 * 5 * 5.5 = 220 for sides areas .... but to include the base we'd have to do some more calculations

  17. anonymous
    • 5 years ago
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    ok well its just asking for the surface area.... LA + B

  18. amistre64
    • 5 years ago
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    this is what I got so far; I can calculate the missing parts the hard way... but thats just how I role lol

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  19. anonymous
    • 5 years ago
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    ha oh boy

  20. amistre64
    • 5 years ago
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    16^2 = 2s^2 -2s^2 cos(74) 16^2 = s^2(2-2cos(74)) 16^2 -------- = s^2 2-2cos(74) Area in red = (s^2 sin(74))/2

  21. anonymous
    • 5 years ago
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    oh wow... so um... tell me you get 200 LOL

  22. amistre64
    • 5 years ago
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    :) I get about 85 there ... if I did it right but *5 gotta chk it again make sure I aint messed it up

  23. amistre64
    • 5 years ago
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    hah!! i had 72 but used 74 lol .....

  24. anonymous
    • 5 years ago
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    ok I'll check again too... good eye

  25. amistre64
    • 5 years ago
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    I get abt 440.5 for the bottom area that way

  26. anonymous
    • 5 years ago
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    i wonder if there is a calculator to find the area... let me investigate LOL

  27. amistre64
    • 5 years ago
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    i think I see an easier way; tan(54) = h/8 h = 8 tan(54)

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  28. amistre64
    • 5 years ago
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    16/2 = 8 8 * 8tan(54) = area of red tri 5* area red tri = area base

  29. amistre64
    • 5 years ago
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    = 215.6

  30. amistre64
    • 5 years ago
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    220 215.6 ------- 435.6 abt for the surface areas

  31. anonymous
    • 5 years ago
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    hey whats the side length, and what is the slant length

  32. anonymous
    • 5 years ago
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    is 10 slant and 8 side

  33. amistre64
    • 5 years ago
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    the side length of the pyramid is 10; and the slant is 5.5

  34. amistre64
    • 5 years ago
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    that 215.6 is off

  35. anonymous
    • 5 years ago
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    I thought the apothem was 5.5

  36. amistre64
    • 5 years ago
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    aint that the slant?

  37. amistre64
    • 5 years ago
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    http://www.wolframalpha.com/input/?i=area+pentagon+side+%3D16 I keep coming to 440.442 as area of base

  38. anonymous
    • 5 years ago
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    the calculator is asking for apothem length side length slant length enter height

  39. anonymous
    • 5 years ago
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    http://easycalculation.com/area/pyramid.php pentagonal pyramid

  40. amistre64
    • 5 years ago
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    5.5 16 10 is what I used

  41. amistre64
    • 5 years ago
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    Sa = 620 .... 220 440.5 ------ so we are close 660.5

  42. amistre64
    • 5 years ago
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    edge base length is what I cant be to sure about; how do you describe that?

  43. anonymous
    • 5 years ago
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    ha your awesome.... hey it says round to the nearest tenth unit...

  44. anonymous
    • 5 years ago
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    the edge where the number is in my book LOL on AB?

  45. anonymous
    • 5 years ago
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    thats my lingo... lol

  46. anonymous
    • 5 years ago
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    I was trying to describe whatever you were asking

  47. amistre64
    • 5 years ago
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    :) does my interpretation for this look good then?

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  48. amistre64
    • 5 years ago
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    if I got the 8 in the right place... then im good to go

  49. anonymous
    • 5 years ago
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    the 8s are at the bottom of base of the pyramid

  50. amistre64
    • 5 years ago
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    yes; the red is just a reflection into the base under the pyramid

  51. anonymous
    • 5 years ago
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    where alll the edges meet and creat the pentagonal base

  52. amistre64
    • 5 years ago
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    yes

  53. anonymous
    • 5 years ago
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    A is the top of the pyramid.... and B is at the bottom with the 8s

  54. anonymous
    • 5 years ago
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    AB is a side of one of them triangles

  55. amistre64
    • 5 years ago
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    the tiny dancer is what I have pictured

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  56. anonymous
    • 5 years ago
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    well there it is!!! yep looks just like it LOL

  57. amistre64
    • 5 years ago
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    then: Sa = 5(face area) + 5(redbase area) Sa = 5(5.5*16/2) + 5(8*8tan(54)/2) Sa = 660.442

  58. amistre64
    • 5 years ago
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    16*8tan(54)/2 lol

  59. anonymous
    • 5 years ago
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    oh wow...

  60. amistre64
    • 5 years ago
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    we got a way to verify this?

  61. anonymous
    • 5 years ago
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    yea that calulator if I know the right numbers

  62. anonymous
    • 5 years ago
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    I dunno... I'm going with what you did!

  63. amistre64
    • 5 years ago
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    ive been trying to define apothem, slant heaight, and all that stuff; but nothing is consistant. apothem of a pyramid most likely means the height of a face; slant height also means distance up the face; so I cant seem to determine what any of it really means..

  64. anonymous
    • 5 years ago
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    85.8253 slnat height is 10? and sides are 5

  65. amistre64
    • 5 years ago
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    do you know how to do a screenshot?

  66. anonymous
    • 5 years ago
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    no

  67. amistre64
    • 5 years ago
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    do you see the "PrtScrn" key that you never use up there with the "pause", and "scroll lock" keys? press it

  68. anonymous
    • 5 years ago
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    k

  69. amistre64
    • 5 years ago
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    now open up your 'paint' program and hit your 'ctrl + v' keys to paste it. and let me know if it worked

  70. anonymous
    • 5 years ago
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    yes

  71. amistre64
    • 5 years ago
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    save it to your desktop as a jpeg and attach it to this post

  72. anonymous
    • 5 years ago
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  73. anonymous
    • 5 years ago
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    is that what you wanted?

  74. amistre64
    • 5 years ago
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    yep; now do that to the screen that has the problem on it :)

  75. anonymous
    • 5 years ago
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    the problem is is in my book

  76. amistre64
    • 5 years ago
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    can you take a picture of it? and put it on the computer? maybe a scanner?

  77. anonymous
    • 5 years ago
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    ok hang on

  78. anonymous
    • 5 years ago
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    ok

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  79. anonymous
    • 5 years ago
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    is that what you wanted LOL

  80. amistre64
    • 5 years ago
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    yes :)

  81. anonymous
    • 5 years ago
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    kk

  82. amistre64
    • 5 years ago
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    the apothem of the pentagon is 5.5 ; thats the length from the center of the base out to the base edge... much better

  83. anonymous
    • 5 years ago
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    just an FYI regular pyramid formula is LA + B Yes , i thought I told you that :)

  84. amistre64
    • 5 years ago
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    this is the correct picture I needed lol

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  85. anonymous
    • 5 years ago
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    I still get 200

  86. amistre64
    • 5 years ago
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    Sa = 5(8*sqrt(10^2+4^2)/2) + 5(8*5.5/2) Sa = 5(4*sqrt(116)) + 5(4*5.5) Sa = 20sqrt(116) + 20(5.5) Sa = 325.406592 ....

  87. anonymous
    • 5 years ago
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    what did we determine the slant length is

  88. amistre64
    • 5 years ago
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    the slant length is the missing leg of the right tri formed by half the base and a hyp of 10 sh^2 + 4^2 = 10^2 sh = sqrt(100 - 16) .. doh!! I added

  89. anonymous
    • 5 years ago
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    9.16

  90. amistre64
    • 5 years ago
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    http://www.wolframalpha.com/input/?i=5%284*sqrt%2810^2-4^2%29%29%2B5%284*5.5%29

  91. anonymous
    • 5 years ago
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    9.17

  92. amistre64
    • 5 years ago
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    Sa = 293.303

  93. anonymous
    • 5 years ago
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    how guaranteed.... I get 366.6

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  94. amistre64
    • 5 years ago
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    is side 10 or 8?

  95. amistre64
    • 5 years ago
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    height should be abt 7.331

  96. anonymous
    • 5 years ago
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    side is the top of pyramid AB 10 no??? whats 8? base I dunno

  97. anonymous
    • 5 years ago
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    who ever invented math is wasting valuable life time for me!!! :(

  98. amistre64
    • 5 years ago
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    ... the base of this thing is abt 110.1111

  99. anonymous
    • 5 years ago
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    thats the perimeter of the base... 5(8) = 40 I thought

  100. amistre64
    • 5 years ago
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    183.303 is the lateral area 110.111 -------- 293.414

  101. amistre64
    • 5 years ago
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  102. anonymous
    • 5 years ago
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    Ok I give up on this one... I am taking your word!

  103. amistre64
    • 5 years ago
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    and this for the base lol

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  104. anonymous
    • 5 years ago
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    you have some neat sites

  105. anonymous
    • 5 years ago
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    when I think I understand .... I DONT!!!

  106. amistre64
    • 5 years ago
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    :) thnx take a break, and get aome air

  107. amistre64
    • 5 years ago
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    I gotta drive up to the veranda and setup for my laptop; librarys closing...

  108. anonymous
    • 5 years ago
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    ok ... I need to review... take my notes... and on to the next.. LOL Thank you

  109. anonymous
    • 5 years ago
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    I'll be here!!

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