Math Help Forum: bearings, triginometry

A helicopter flies on a bearing of 200° from A to B, where AB=70 km. It then flies on a bearing of 150° from B to C, where C is due south of A. Work out the distance of C from A.

can someone please tell me what is wrong with the diagram I have drawn?

The helicopter moves from A to B on a bearing of 200, so the point B should actually be on the other side of A as 200>180.You should end up with a triangle with C directly below A, where AB=70km. you then need to work out angles ABC and BCA so you can use the sine rule to find the length of AC.

Hello, Tweety!

A helicopter flies on a bearing of 200° from to , where km.
It then flies on a bearing of 150° from to , where is due south of .

Find the distance from to

The first leg of the flight looks like this:

Code:

            :
            :
            :
          A *
           /  200°
       70 / 
         /
        /
       /
    B *

The second leg looks like this:

Code:

      :
      :
    B * 150°
      :\
      : \
      :  \
          \
           \
            * C

So the diagram should look like this:

Code:

      :           * A
      :         * |
      :   70  *20°|
      :     *     |
      :20°*       |
      : *         |
    B * 130°      |
      : *         |
      :30°*       |
      :     *     |
      :       *30°|
      :         * |
      :           * C

Originally Posted by Tweety

can someone please tell me what is wrong with the diagram I have drawn?

Hi Tweety,

See diagram. And see Soroban's post for the angles.