The equation that is true is D
Answer:
18.7
Step-by-step explanation:
The Law of Cosines is
, where c is the unknown side length of a triangle, a and b are the remaining two side lengths, and C is the angle opposite to side c. To answer this question just plug in the known values:

Simplify:



m≈18.665...
When rounded to the nearest tenth, m=18.7
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If gravity acceleration is 10 :


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If gravity acceleration is 9.8 :



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