To find the distance across a small lake, a surveyor has taken the measurements shown in the figure below. If a = 850 ft, b = 960 ft, and C = 75°, find the distance across the lake.

To solve this question we will use the cosine law:
[tex]c^2=a^2+b^2-2ab\cos C.[/tex]c is the distance we are looking for and we are given that a=850, b=960, and C=75°. Substituting those values in the above equation we get:
[tex]\begin{gathered} c^2=(850^2+960^2-2(850)(960)\cos 75^{\circ})ft^2, \\ c^2=1221707.318ft^2. \end{gathered}[/tex]Therefore:
[tex]c=1105.308698\text{ ft.}[/tex]Answer: third option.