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Mathematics 18 Online
OpenStudy (anonymous):

Find total area for the regular pyramid.

OpenStudy (anonymous):

OpenStudy (anonymous):

|dw:1365042935605:dw|

OpenStudy (anonymous):

|dw:1365043084717:dw|

OpenStudy (anonymous):

@jim_thompson5910

jimthompson5910 (jim_thompson5910):

each triangle has an area of 4*6/2 = 12 square units there are 6 of them, so the lateral surface area is 6*12 = 72 square units

jimthompson5910 (jim_thompson5910):

you just need to find the area of the base to get the total surface area

OpenStudy (anonymous):

Thats what I'm having problems with. I don't know how to find the base for a hexagonal pyramid.

jimthompson5910 (jim_thompson5910):

let's rotate the 3D figure and look directly at the hexagonal base

jimthompson5910 (jim_thompson5910):

if we do that, we get |dw:1365044143031:dw|

jimthompson5910 (jim_thompson5910):

now divide this hexagon up into triangles |dw:1365044186805:dw|

jimthompson5910 (jim_thompson5910):

each triangle is an equilateral triangle with side length of 4

jimthompson5910 (jim_thompson5910):

so you can use this formula A = (1/4)*sqrt(3)*s^2 where s = side length to find the area of each triangle

OpenStudy (anonymous):

got 4sqrt3

jimthompson5910 (jim_thompson5910):

that's the area of one triangle but there are 6 of them (that are the same area) so the hexagon has a total area of 6*4*sqrt(3) = 24*sqrt(3) square units

jimthompson5910 (jim_thompson5910):

total surface area = (Base Area) + (Lateral Surface Area) total surface area = (24*sqrt(3)) + (72) total surface area = 24*sqrt(3) + 72 total surface area = 72 + 24*sqrt(3)

OpenStudy (anonymous):

Thank you soo much!!

jimthompson5910 (jim_thompson5910):

you're welcome

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