Question

An airplane over the Pacific Ocean sights an atoll at an 7° angle of depression. If the plane is 850 m above the water, how many kilometers is it from a point 850 m directly above the atoll?

Answer 1

Draw a diagram. You will see that

x/850 = cot 7°

Now solve for x
Don't forget that x is in meters, so divide by 1000 to answer in km.