Thread: bearing

Im not sure how to draw this and so i havnt been able to try and solve it yet, so if you could help me draw it and give a few hits that would be great thnx

A ship travelling with a constant speed and direction is signhted from a lighthouse.At this time it's 2.7kn away on a bearing of 42degrees. half an hour later it is ona bearing of 115degrees at a distence of 7.6 km from the same lighyhouse. find its speed in km per hour

thank you

Hello, Chez_!

A ship travelling with a constant speed and direction is signhted from a lighthouse.
At this time it's 2.7km away on a bearing of 42°.
Half an hour later, it is on a bearing of 115° at a distence of 7.6 km.
Find its speed in km per hour

Code:

      N       A
      :       *
      : 42° *  \
      :   *2.7  \
      : *        \
    L * 73°       \ x
         *         \
            *       \
            7.6*     \
                  *   \
                     * \
                        * B

Bearings are measured clockwise from North.

The lighthouse is at

The ship is first sighted when

The ship is sighted next when
. . and

We want the distance:


In , use the Law of Cosines:
. .

Hence: .

Now you can calculate its speed, right?