An airplane is flying at 500km/hr in a wind blowing 60 km/hr toward the SE.
In what direction should the plane head to end up going due east?
What is the plane's speed relative to the ground?
* | *
500 * | * 60
* |h *
* | *
* θ | 45° *
A * * * * * * * * * * C
: - - - - - - - - b - - - - - - - - :
The plane flies from to at 500 km/hr.
The wind is blowing from to at 60 m/hr.
The result flight is , directly east.
In the right triangle at the right: . 
In the right triangle at the left: . 
Substitute  into : .
The direction should be about: . north of east.
We have: .
Law of Sines: .
Its ground speed is about: . km/hr.