Problem 9, part a)
Compass bearings always have north as the starting point. This is where 0 degrees is situated, and 360 degrees as well. As the bearing angle increases, you'll turn to the right toward the eastward direction. Effectively you're sweeping out a clockwise rotation. The bearing 322 degrees is in a northwest position as the diagram shows (place the ship at the bottom right corner of the triangle). The bottom right acute angle of the triangle is 322 - 270 = 52 degrees. This is the reference angle we'll use for finding the distance d.
With respect to the reference angle of 52 degrees, the side 18.5 is the opposite side and d is the adjacent side. Use the tangent ratio to get...
tan(angle) = opposite/adjacent
tan(52) = 18.5/d
d*tan(52) = 18.5
d = 18.5/tan(52)
d = 14.4537840903742
The approximate value of d is 14.4537840903742 km
This rounds to 14.5 when rounding to one decimal place.
Answer: 14.5 km
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Problem 9, part b)
Recall that
distance = rate*time
where "rate" is another term for "speed" or "velocity"
We can solve this for the time to get
time = distance/rate
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We found the distance back in part a) above. We are given the rate of 48 km/h
So,
time = distance/rate
time = 14.4537840903742/48
time = 0.3011205018828
This is the time it takes in hours. Multiply by 60 to convert to minutes
0.3011205018828 hours = 60*0.3011205018828 = 18.067230112968 minutes
This rounds to the whole number 18
Answer: 18 minutes
