anonymous
  • anonymous
Someone please help with surface area of pyramids and cones
Mathematics
  • Stacey Warren - Expert brainly.com
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SOLVED
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jamiebookeater
  • jamiebookeater
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anonymous
  • anonymous
are these answers correct? the first one i got 282.6m^2 the second one i got 175.84in^2
amistre64
  • amistre64
if you can cut the cone up its lengthand make into part of a circle, the surface area is easy to get :) maybe even easy if I think about it some
amistre64
  • amistre64
is the 10 inches the length up the side of the cone or the height?

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anonymous
  • anonymous
length
anonymous
  • anonymous
its actually slant height
amistre64
  • amistre64
then that 10 inch length is the radius of a larger circle, find its circumference" 2pi10 20pi is its curcumference the small base circle is the length of the circumference that you want to find an area for 2pi4 = 8pi make sense?
anonymous
  • anonymous
kinda
anonymous
  • anonymous
\[s =\pi \times r ^{2}+\pi \times r \times l\] is the formula i need to use
amistre64
  • amistre64
length of an arc = theta(r) 8pi = theta(10) theta = 8pi/10 = 4pi/5 area of sector = theta r^2/2 (4pi/5)(10)(10)/2 200/5 = 40pi fpr the surface area of the cone, do we include that base in this or not?
amistre64
  • amistre64
40pi + 16pi = 56pi if I did it right :)
anonymous
  • anonymous
ok
anonymous
  • anonymous
would = 175.84in^2
amistre64
  • amistre64
175.92 is what I get... is that close enough?
amistre64
  • amistre64
175.84 if you use (3.14)
anonymous
  • anonymous
yea
anonymous
  • anonymous
how would i find the surface area of this one
1 Attachment
amistre64
  • amistre64
if im doing it right, I get 85pi
anonymous
  • anonymous
would i use half the diameter?
amistre64
  • amistre64
if you dont have answers to check against, I would suggest gettting a second opinion :) but yes, radius is half the diameter
anonymous
  • anonymous
\[s =\pi \times 5^{2}+\pi \times 5 \times 12\]
amistre64
  • amistre64
i got 25pi + 60pi too :)
amistre64
  • amistre64
im glad the formula works :)
anonymous
  • anonymous
witch would = 266.9ft^2
anonymous
  • anonymous
would you please help me with three more
amistre64
  • amistre64
i could try.... getting kinda deer in the headlights feeling....must.....carry.........on. . . . . . . ok
anonymous
  • anonymous
find the surface area of the regular pyramid
amistre64
  • amistre64
#31 3cm is pointing to what?
anonymous
  • anonymous
3cm is height i believe
amistre64
  • amistre64
is it face height or pyramid height?
anonymous
  • anonymous
the formula for this on is S=B+1/2Pl
anonymous
  • anonymous
looks like pyramid hight
amistre64
  • amistre64
pyramid height would have a dotted line stricking down the middle of it..... i think its face height.
anonymous
  • anonymous
so do i
amistre64
  • amistre64
4cm^2 + 12 cm^2 = 16 cm^2 for #31
amistre64
  • amistre64
#32...all I see is a 7 and not much else for details...
anonymous
  • anonymous
thats all there is
amistre64
  • amistre64
is that all sides are 7? like an equalateral triangle?
anonymous
  • anonymous
yea
amistre64
  • amistre64
then I would do: 4 times (1/2)(49)sin(60) 84.87 m^2
amistre64
  • amistre64
if you have a side-angle-side, the area can be determined by: (side)(side)(sin(angle))/2 and there are 4 sides so I timesed it by 4 :)
amistre64
  • amistre64
(side)sin(a) = height, and the other side = base
anonymous
  • anonymous
ok
amistre64
  • amistre64
and for the last one its just like the first except with decimals..
amistre64
  • amistre64
(9.2)^2 + 4(9.2)(13)/2
amistre64
  • amistre64
84.64 + 239.2 = 323.84
anonymous
  • anonymous
okay thank you so much
amistre64
  • amistre64
youre welcome :)

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