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AcidRa1n

  • 3 years ago

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  1. AcidRa1n
    • 3 years ago
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  2. AcidRa1n
    • 3 years ago
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    Ok how does angle C equal 20 and PS is 5?

  3. AcidRa1n
    • 3 years ago
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    Unkle it's not that hard come on...

  4. UnkleRhaukus
    • 3 years ago
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    there are 360° in a complete revolution, angle C is 1 eighteenth of the wayround \[\angle C=360°/18\]

  5. AcidRa1n
    • 3 years ago
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    wait what so how its it 20 on there?

  6. UnkleRhaukus
    • 3 years ago
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    did you simplify \(\angle C =\frac{360°}{18}=\dots\)

  7. AcidRa1n
    • 3 years ago
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    ohhh

  8. UnkleRhaukus
    • 3 years ago
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    \[36=2\times18\] \[360=2 \times 18\times10\]

  9. AcidRa1n
    • 3 years ago
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    How would you find the area?

  10. UnkleRhaukus
    • 3 years ago
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    well the shape can be see as 18 of those little right angled triangle joined together, find the area of one then multiply by 18

  11. UnkleRhaukus
    • 3 years ago
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    |dw:1338432746562:dw|

  12. AcidRa1n
    • 3 years ago
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    ok wait

  13. AcidRa1n
    • 3 years ago
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    I have a diferent problem on my notes.. Same shape but it says each side = 4

  14. AcidRa1n
    • 3 years ago
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    What is the area.

  15. AcidRa1n
    • 3 years ago
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    |dw:1338433164896:dw|

  16. AcidRa1n
    • 3 years ago
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    like that

  17. UnkleRhaukus
    • 3 years ago
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    you can find length CS = a using a trigonometric function of the angle 20°

  18. AcidRa1n
    • 3 years ago
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    Lets say the question only give you the length of one side is 4

  19. AcidRa1n
    • 3 years ago
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    How would you go about finding the area?

  20. UnkleRhaukus
    • 3 years ago
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    |dw:1338432905847:dw|

  21. AcidRa1n
    • 3 years ago
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    |dw:1338433361442:dw|

  22. AcidRa1n
    • 3 years ago
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    Thats all it gives you. Find the area. I know it has something to do with finding the apothem and finding the perimeter and using the TAN function.

  23. AcidRa1n
    • 3 years ago
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    Half of one side is 2.

  24. UnkleRhaukus
    • 3 years ago
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    \[\tan(20°)=\frac{\text{opposite}}{\text{adjacent}}=\frac5a\] \[a=\frac 5{\tan(20°)}\neq4\]

  25. UnkleRhaukus
    • 3 years ago
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    or is the 4 coming from a different problem/

  26. UnkleRhaukus
    • 3 years ago
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    the diagram posed at the top of the page does not have any side- length equal to 4

  27. AcidRa1n
    • 3 years ago
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    4 from a different problem

  28. UnkleRhaukus
    • 3 years ago
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    OK, what is the new problem exactly/

  29. AcidRa1n
    • 3 years ago
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    What I drew that's all it gives me

  30. AcidRa1n
    • 3 years ago
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    A decagon with a side lengths of 4. Find the Area.

  31. UnkleRhaukus
    • 3 years ago
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    well the first one was a nonagon so the picture is wrong

  32. AcidRa1n
    • 3 years ago
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    RAWRRRRRRRRR I HATE MATH SO MUCH OMFG

  33. UnkleRhaukus
    • 3 years ago
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    |dw:1338433609250:dw|

  34. AcidRa1n
    • 3 years ago
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    I DONT HAVE TIME FOR THISSSS I WANNA SLEEP

  35. AcidRa1n
    • 3 years ago
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    Yes now find the area. Just with that information.

  36. UnkleRhaukus
    • 3 years ago
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    well should i sing you a lullaby instead ?

  37. AcidRa1n
    • 3 years ago
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    LOL

  38. UnkleRhaukus
    • 3 years ago
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    ok so you might want to find the angle in triangle first, remember there are 360° in a revolution and i count 10 angles, so the angle in is \[360°/10\]

  39. UnkleRhaukus
    • 3 years ago
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    next find the length of the perpendicular , using the angle you just found and the tangent function

  40. UnkleRhaukus
    • 3 years ago
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    |dw:1338433908040:dw|, find the area of the triangle and lastly multiply this area by the number of those triangles in the decagon

  41. AcidRa1n
    • 3 years ago
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    360/10 =36? When I apply the TAN to 36 it's weird...

  42. AcidRa1n
    • 3 years ago
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    @UnkleRhaukus

  43. UnkleRhaukus
    • 3 years ago
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    true, what did you determine as an approximation of length b

  44. UnkleRhaukus
    • 3 years ago
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    2 significant figures is probably fine

  45. AcidRa1n
    • 3 years ago
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    huh? I didnt get that far becuase I thought you need to know the TAN of 36

  46. AcidRa1n
    • 3 years ago
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    @satellite73

  47. UnkleRhaukus
    • 3 years ago
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    yeah \[\tan(36°)\approx0.727\]

  48. AcidRa1n
    • 3 years ago
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    ok.. Let me see

  49. UnkleRhaukus
    • 3 years ago
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    \[\tan(36°)=\frac{\text{opp}}{\text{adj}}=\frac 2 b\] \[b=\frac {2}{\tan36°}\approx\cdots\]

  50. AcidRa1n
    • 3 years ago
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    why is it b= 2/tan36?

  51. AcidRa1n
    • 3 years ago
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    Ohh I got it

  52. AcidRa1n
    • 3 years ago
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    so its 2.75

  53. UnkleRhaukus
    • 3 years ago
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    we are trying to find \(b\) so we can work out the are of the triangle \[\tan(36°)=\frac{\text{opp}}{\text{adj}}=\frac 2 b\] multiply both sides by \(b\) then divide both sides by \(\tan36°\)

  54. UnkleRhaukus
    • 3 years ago
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    yes \(b\approx 2.75\)

  55. AcidRa1n
    • 3 years ago
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    so then after we find the area which is 2.752 we take the perimeter which is 40, and do 1/2* 2.752* 40

  56. UnkleRhaukus
    • 3 years ago
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    find the area of this triangle |dw:1338435087210:dw|

  57. UnkleRhaukus
    • 3 years ago
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    \[A_{\triangle}=\frac{ab}2=\frac {2b}2=\cdots\]

  58. UnkleRhaukus
    • 3 years ago
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    you dont need the perimeter

  59. AcidRa1n
    • 3 years ago
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    My notes has it O.o

  60. AcidRa1n
    • 3 years ago
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    Maybe hes teaching it like that?

  61. AcidRa1n
    • 3 years ago
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    THe formula for Area is. 1/2 * Apothem * perimeter

  62. UnkleRhaukus
    • 3 years ago
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    whatever, my method is better ~ so the area of the small right angled triangle is 2.752 and there are 20 of these in the decagon the the total area is simply \(A_{decagon}=2.752\times20=\cdots\)

  63. AcidRa1n
    • 3 years ago
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    Yeah lol same thing I got.

  64. AcidRa1n
    • 3 years ago
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    Well, thanks for taking like 30 minutes of your time to help me lol.

  65. AcidRa1n
    • 3 years ago
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    I'm so dumb.

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