I encountered the question below on a national-level high school test that took place today.
"Two ships, A and B, depart from the port at the same time. A sails at 8 km/h on a 120 degree course. B sails on a 195 degree course. After 90 min, the course from A to B is 255 degrees. What's the speed of B?
From my point of view the information provided seems scant. We only know that ship A has sailed for 12 km on a course 120 degrees starting from the first quadrant and that after 90 min ship B sails on a course of 15 degrees(not sure on that considering the confusing language of the problem). I was thinking of the cosine theorem but we don't know the distance from A to B. Could you provide some insight on the hidden data and possibly a solution to this problem?
Like I said in a comment, you’re not seeing the third angle.
It is now a simple application of the sine rule.
Edit: clarification figure