Patrick is building a patio in the shape of a decagon with a radius of 12 feet. To determine the amount of cement needed, he must first find the area.

Respuesta :

Answer:

The area of the Patrick's building is [tex]2340.22 ft^2[/tex].

Step-by-step explanation:

Shape of the Patrick's building = Decagon

In the figure attached:

Radius of the decagon = r = 12 feet

Side of the decagon = a

Angle AOB = 36°

Using trigonometric ratio is triangle AOC :

AO = r = 12 feet

AC = [tex]\frac{a}{2}=0.5a[/tex]

[tex]\tan \theta=\frac{Perpendicular}{base}[/tex]

[tex]\tan 36^o=\frac{0.5a}{12 feet}[/tex]

[tex]a=\frac{\tan 36^o\times 12 feet}{0.5}=17.44 feet[/tex]

Area of decagon :

[tex]A=\frac{5}{2}a^2\times \sqrt{5+2\sqrt{5}}[/tex]

[tex]A=\frac{5}{2}(17.44 ft)^2\times \sqrt{5+2\sqrt{5}}[/tex]

[tex]A=2340.22 ft^2[/tex]

The area of the Patrick's building is [tex]2340.22 ft^2[/tex].

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