Answer is 11.9ft.
Law of cosines:
In trigonometry, the Cosine Rule says that the square of the length of any side of a given triangle is equal to the sum of the squares of the length of the other sides minus twice the product of the other two sides multiplied by the cosine of angle included between them.
[tex]c^{2} = a^{2} + b^{2} - 2ab cos(C)[/tex]
Since we have two side lengths and an angle, we can use the Law of Cosines to find the length of the final side.
In this case we can write the law of cosines as,
[tex]f^{2} = d^{2} + e^{2} - 2(de)cos(F)[/tex]
f2 = 5.22 + 6.82 - 2(5.2)(6.8)cos(166)
f2 = 27.04 + 46.24 - 66.56 cos (166)
f2 = 73.28 - 66.56 cos 166
f = √(73.28 - 66.56 cos 166) ≈ 11.9 ft.
f ≈ 11.9 ft.
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