physics
posted by Elisa .
An airplane flies 200 km due west from city A to city B and then 280 km in the direction of 30.5° north of west from city B to city C.
(a) In straightline distance, how far is city C from city A?
(b) Relative to city A, in what direction is city C?
The answer is: 17.8 degrees north of west
I received help with this question before, but I keep getting the wrong answer for (a).

Show us what you did.

okay: I got the vector from A to B and then the vector from B to C to get the distance from A to C.
I got 200.00 from the vector from A to B and then 280.00 from the vector from B to C. I added them, but the answer is incorrect.
For A to B: I did 200cos30.5
200sin30.5
Then I did the pythagorean and got 200.00
For B to C: I did 280cos17.8
280sin17.8
Pythagorean and got 280.