Hi,

I am trying to teach myself trig from a book and have come across the following question that I cannot seem to get the right answer for...

Two ships leave port at the same time. The first steams on a bearing 135 degrees at 18km/h and the second on a bearing of 205 degrees at 15km/h. Calculate the time that will have elapsed when they are 86km apart.

The book gives the answer as 4.51 hours but I can't get this.

I have tried using the cosine formula and end up with a quadratic equation which when solved does not give me the correct answer. Am I overcomplicating the method?

Thanks for any help