Answer:
The boat turned 39° degrees when it made its first turn.
Explanation:
The question is as following:
A boat traveled north for 28 miles, then tuned x° south west and traveled for 25 miles before stopping. When it stopped, the boat was 18 miles from its starting point.
By how many degrees did the direction of the boat change when it made its first turn? Round to the nearest degree.
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See the attached figure which represent explanation of the problem.
The boat start from point A to point B then stopped at point C
AB = 28 miles, BC = 25 miles and AC = 18 miles.
It is required to find the angle x
By applying the cosine Rule:
AC² = AB² + BC² - 2 * AB * BC * cos x
18² = 28² + 25² - 2 * 28 * 25 * cos x
2 * 28 * 25 * cos x = 28² + 25² - 18²
1400 cos x = 1085
Cos x = 1085/1400 = 0.775
x = Cos⁻¹ 0.775 = 39.2° = 39° to the nearest degree.
So, the boat turned 39° degrees when it made its first turn.