The appropriate shape to model trunk is cylinder, rest of the tree is cone and surface area of trunk is 25.12 [tex]feet^{2}[/tex]and surface area of rest of the tree is 415.58 [tex]feet^{2}[/tex].
What is surface area?
It is the space occupied by a two dimensional surface. The area occupied by a three dimensional object by its outer surface area.
How to calculate surface area?
The upper part of the tree is similar to the cone and the trunk is of cylindrical shape. So the appropriate shape used to model the entire is cone above the cylinder.
We have been given the height of entire tree=30 feet,
Width of upper part=10 feet.
Height of trunk=4 feet
Width of tree means diameter of upper part or cone. Height of cone means height of cylinder, width of trunk means diameter of cone.
So, The radius of cone ie 5 feer,radius of cylinder is 1 feet, height of cone be 30-4=26 feet.
Surface area of cone is πrl where l is slant height of cone which is equal to [tex]\sqrt{r^{2} +h^{2} }[/tex]
l=[tex]\sqrt{5^{2} +26^{2} }[/tex]
=[tex]\sqrt{701}[/tex]
=26.47 feet.
Surface area of cone=π*5*26.47
=3.14*5.26*26.47
=415,28 [tex]feet^{2}[/tex]
Surface area of cylinder=2πrh
=2π*4*1
=2*3.14*4
=25.12 [tex]feet^{2}[/tex]
Hence cone and cylinder of surface area 415.28 [tex]feet^{2}[/tex] and 25.12 [tex]feet^{2}[/tex] can be used to model out tree.
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