Question: A plane is 120 miles north and 85 miles east of an airport. If the
pilot wants to fly directly to the airport, what bearing should be
taken?
Answer: Draw a right-angled triangle ABC with A the airport. B is due
north of A and AB = 120 miles. C is due east of B and BC = 85 miles.
We wish to calculate angle BAC. With this as our reference angle, AB
is the 'adjacent' side and BC is the 'opposite' side. Then we use the
trig. ratio 'tan' to write down the equation
tan(BAC) = opposite/adjacent
= BC/AB = 85/120 = 0.708333
To find the angle whose 'tan' is 0.708333 we use the INVERSE tan
function, and this gives angle(BAC) = 35.31 degrees
This is the direction going from the airport to the aircraft.
However, we want the direction from the aircraft to the airport. This
is the reciprocal of 35.31, and is found by adding 180 degrees, so the
direction from aircraft to airport is 35.31 + 180 = 215.31 degrees.
This is definitive proof that GTM should update this thread more regularly.
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2014 F150 Raptor, 2014 Mazda 3, 2015 Nissan GT-R
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