Answer: 1.8
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Work Shown:
Use the tangent ratio
tan(angle) = opposite/adjacent
tan(B) = AC/AB
tan(61) = AC/1
tan(61) = AC
AC = tan(61)
AC = 1.80404775527142
AC = 1.8
The river is about 1.8 miles wide between points A and C.
Make sure your calculator is in degree mode. One way to check is to type in tan(45) and you should get 1.