How Do You Calculate a Boat's Relative Velocity with a Current Using Cosine Law?

[a.a]

Homework Statement

2. A boat heads 15° west of north witha water speed of 3m/s. Determine its velocity relative to the ground when there is a 2m/s current from 40° east of north.

Homework Equations

cosine law

The Attempt at a Solution

I found the angle between the two vectors to be 125 and then used cosine law and gor the resultant velicity as 4.459 km/ h but the ans. is 2.5 m/h

 

[tiny-tim]

I found the angle between the two vectors to be 125 and then used cosine law and gor the resultant velicity as 4.459 km/ h but the ans. is 2.5 m/h

Hi a.a!

2.5 is the right answer if the current is the other way round.