Which of the following is the closest approximate area of the figure shown above? It is the difference between two isosceles trapezoids whose corresponding sides are parallel.
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tan θ = 8 3 ⟹ θ ≈ 2 2 . 5 5 6
cos 2 0 . 5 5 6 = x 3 ⟹ x = cos 2 0 . 5 5 6 3 ⟹ x ≈ 3 . 2 0 4
By similar figures, we have
8 3 = 5 y ⟹ y = 8 3 ( 5 ) 8 1 5 = 1 . 8 7 5
Let A B be the area of the big trapezoid and A S be the area of the small trapezoid. Then
A B = 2 1 ( 1 4 + 2 0 ) ( 8 ) = 1 3 6
A S = 2 1 ( 9 . 8 4 2 + 1 3 . 5 9 2 ) ( 5 ) ≈ 5 8 . 5 8 5
Finally the area of the figure is 1 3 6 − 5 8 . 5 8 5 ≈ 7 7