Use the Law of Cosines here with angle A as your reference angle. It will be the one that the helicopter is at, the one we are looking for. If that angle is angle A, then the side across from it is a, measure of 11.4. Here's how the Law looks in our particular situation: [tex](11.4) ^{2}=(7.4) ^{2} +(8.5)^2-2(7.4)(8.5)cos(A)[/tex]. Simplifying a bit we get 129.96 = 54.76 + 72.25 - 125.8cos(A) Combining like terms across the equals sign gives us 2.95 = -125.8 cosA. Doing the division we get -.0234499205 = cosA. Find the angle using the 2nd and cos buttons on your calculator. It's 91.34°, rounded to just 91°. Choice A
