An airplane leaves a runway heading due east then turns 35 degrees to the right as shown in the figure. How much more will the airplane have to turn to be heading due south?
Because the plane is flying due east, it has to turn 90º to face south, before it turns the extra 35.31º to fly towards the airport. 90° + 35.31° = 125.31º It actually turns through the exterior angle of the triangle :
You want to know the additional angle a plane must turn through to be going south after it took off going east, then turned right 35°.
Bearing
The initial bearing angle was 90° (straight east). After turning right 35°, the airplane now has a heading of (90+35)° = 125°. To be going south (180°), the bearing must increase by ...
180° -125° = 55°
The airplane will have to turn 55° more to be heading due south.
