Cos y = 16 / 17.89 = 0.8944
y = cos^-1 (0.8944) = 26.57°
tan 26.57 = BA / 17.89
BA = 17.89 tan 26.57 = 8.95
tan x = 17.89 / 8.95 = 1.999
x = arctan 1.999 = 63.43
sin x = sin 63.43 = 0.8944
Everything is in million acres, so we can just drop that while we work it out but just remember we have to add it back on at the end of the problem.
First year 3.42
Second year 8.71
Third year ???
Total 21.46
So...
3.42 + 8.71 + ? = 21.46
12.13 + ? = 21.46
? = 21.46 - 12.13
? = 9.33
The 3rd year 9.33 million acres were burned
*Note I put a ? for the unknown. I could have used x or y or anything else.
Answer: 
which is Choice A
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Work Shown:
Let 
So,
This therefore means:
as long is x is nonnegative.
