Respuesta :

area of trapezoid = (1/2)(B + b)h

where B = length of one base; b = length of the other base; h = height

You have

b = 12 ft (the upper base)

B = 8.7 ft + 12 ft = 20.7 ft (the lower base)

Now we need the height, h. The triangle has a right angle and a 30-deg angle, so the third angle must measure 60 deg. It is a 30-60-90 triangle. In a 30-60-90 triangle, the hypotenuse is trwice the length of the shourt leg. The height of the trapezoid is the short leg of the triangle.

h = (10 ft) /2 = 5 ft

The height of the trapezoid is 5 ft.

area of trapezoid = (1/2)(20.7 + 12)(5) ft^2

area = 81.75 ft^2

Answer: 81.75

we know that Area of a trapezoid [tex] =1/2(a+b)*h [/tex]

[tex] a [/tex] and [tex] b [/tex] are parallel sides

[tex] h [/tex] is the height or altitude of the trapezoid

we have [tex] a=8.7+12=20.7 ft [/tex]

[tex] b=12 ft [/tex].

we need to find [tex] h [/tex] by using pythagorean identity.

[tex] (hypotensue)^2=(base)^2+(altitude)^2 [/tex]

[tex] altitude=\sqrt{(hypotensue)^2-(base)^2} [/tex]

[tex] altitude=h=\sqrt{(10)^2-(8.7)^2} =4.93ft [/tex]

area of the trapezoid [tex] =1/2(20.7+12)*4.93=80.61ft^2 [/tex]