The angle from which helicopter take off approximately equals 11.30993247;
Answer:
Points C,D, E and F are coplanar.
We can solve for the length of side a to the nearest whole number using the Laws of Cosines such as the formula is shown below:
a²=b²+c²-2bcCosA
Solving for the value of a, we have:
a²=10²+14²-2(10)(14)cos54°
a²=131.42
a=11.46
The answer is 11.46 or 11.5.